Guessing 250 to 275 hp depending on the heads. A 60cc head will reduce compression.

About that rear main seal.  No machining is required to eliminate the rope seal. Simply remove the “nail” from the bearing cap and install a good felpro viton two piece seal. They work very well and are NOT a rope seal. Be sure to clock it 3/8” in the block and cap so the end joints are not even with the block/cap parting surface. Do NOT put any sealer on the seal, but put a paper thin layer of rtv on the main cap surface outside of the seal area to keep oil from traveling through the parting surface.

Go with the 5.0 roller block.

289 heads 58cc
J code 68 were 53, if I remember right.

Are you really going to race it?  Or do you just want a stout street performer?  Nowadays, I am more concerned with the darn thing holding together without constantly having to work on it than I am with getting that last few hp out of it.

Thanks for the input guys! Much appreciated.
With regards to compression, I would definitely address this by the recommended methods.
Ultimately I hope to build an engine with 300-325 horsepower.
I agree with what you said MS... I have always been about a reliable cruiser. Not a race car or anything like that. I want something that I just turn the key and it runs nicely and reliably. I also want it to be smooth at 65-70 mph. I'm definitely not wanting anything wild and I still want reasonable fuel economy.
With the 5.0 block, you guys might talk me into that. I guess with mine being a D code and it having the original engine and transmission, a part of me feels not right about ditching the original engine.

If you go for the 5.0, you will not be able to use your z-bar clutch linkage.  The mounting bung is not on the block in later engines.  There is a fixture you can get from most parts stores to allow the z-bar linkage.

lowercasesteve wrote:

If you go for the 5.0, you will not be able to use your z-bar clutch linkage.  The mounting bung is not on the block in later engines.  There is a fixture you can get from most parts stores to allow the z-bar linkage.

Thanks for sharing this, that is interesting to know! Is there a part description on what someone would need to keep the z-bar set up?

300HP from a 289 is easily acheiveable.  You are only asking just over 1HP/cubic inch.  Every engine I've built in the past two decades has made 1.2-1.5 HP per cubic inch, and I don't consider any of them to be unstreetable or a PITA.

That said, you will have more average power and particularly torque (especially with a smaller engine) by using a roller cam, and that's a cheaper proposition with a 5.0 vs. a 289.  I haven't touched a flat tappet cam in 2 decades and its doubtful I ever will again.

Parts selection is critical, and if you want the best of both worlds its going to come at a cost.  First, el cheapo heads are not going to get it.  Pony up for some AFR 165s.  Set compression at 9.5:1.  Full roller valvetrain.  Have a cam company select the cam (I prefer Crane as their tech department actually picks up the phone).  Good shorty headers and 2.25 or 2.5" exhaust.  Good intake and 600cfm carb.  In a street engine that turns under 6,500RPM the magic is all in the top end.  The bottom end just needs to be properly machined and put together with all clearances checked. 
 

TKOPerformance wrote:

300HP from a 289 is easily acheiveable.  You are only asking just over 1HP/cubic inch.  Every engine I've built in the past two decades has made 1.2-1.5 HP per cubic inch, and I don't consider any of them to be unstreetable or a PITA.

That said, you will have more average power and particularly torque (especially with a smaller engine) by using a roller cam, and that's a cheaper proposition with a 5.0 vs. a 289.  I haven't touched a flat tappet cam in 2 decades and its doubtful I ever will again.

Parts selection is critical, and if you want the best of both worlds its going to come at a cost.  First, el cheapo heads are not going to get it.  Pony up for some AFR 165s.  Set compression at 9.5:1.  Full roller valvetrain.  Have a cam company select the cam (I prefer Crane as their tech department actually picks up the phone).  Good shorty headers and 2.25 or 2.5" exhaust.  Good intake and 600cfm carb.  In a street engine that turns under 6,500RPM the magic is all in the top end.  The bottom end just needs to be properly machined and put together with all clearances checked. 
 

That's great to know TKO! I will probably aim for a more realistic 300HP. Biggest thing for me is drive ability and reliability. I never want some beast that shakes itself to bits at idle and everyone hears you coming. My aim will always be to have a cruiser. A simple and reliable cruiser.
With the heads, that is where I would invest the money like you suggest. Thanks.

I have a template of the z-bar bracket if anyone needs it.

MS wrote:

Also check ebay for that bracket. Lots of fabricators have jumped on the wagon making them for around $60, last time I looked.

I once installed a late model 351w engine that did not have the mount hole fir the z bar. I simply drilled and tapped the side of the block. The 5.0 engines do not have the cast boss on the side to do that, though.

Cable clutch and five speed eliminates that nasty ild z-bar anyway.

Highly recommend the cable clutch .

For a guy like ME........sure!
I'm not sure what kind of compromise YOU  are comfortable with.
For sure it's NOT gonna be silky smooth like a Hyundai  SUV.
These 60's pony cars/performance pieces were meant to be driven...... not just rode in.
   (It's why most HiPo cars of that era were 'driven'/owned by Men).
Jus say'in
6sal6

Fox 5.0s made 225HP, wound to 6,250, and were a blast to drive.  You are only talking about 11 more cubes.  Granted, the EFI will bolster low speed torque, but peak power is going to be almost identical.  Those cars also had a 2.73 rear gear. 

I think its important to understand that the bottom half of the engine doesn't care what decade its in.  The technology available in heads, cams, etc. has improved dramatically in 50 years.  If you go with 60's tech, sure, expect a typical '60s era high performance car that lacks manners.  If you take advantage of the modern tech most of that can be avoided at this power level.  Now, with a carb, sure, you are not going to have as smooth an idle and it will be a bit more high strung (solved with a 3.5-3.73 rear gear and decent gearing in the trans).  This is why I always advise letting a cam company select your cam.  This is also why I advise spending the money on the best heads. 

At some point we need to get away from this totally outdated idea that 1HP per cube is radical.  Its just not anymore.  It was radical when it had to be done with high compression and a solid flat tappet cam.  Once you realize that compression is only worth 5% power per point and that low lift flow through the heads is what really matters, and that that can make up for the lower compression (especially coupled with a roller cam) it comes into focus.  In modern terms let me tell you what 1HP per cube is: a dog.  What Smokey Yunick referred to as an "also ran".  Sure, modern engines make use of a lot of electronic trickery, but most of that is in service to emissions and other concerns.  Bottom line, no modern V8 makes only 1HP per cube.  Most are a lot closer to 1.5.  You are looking to make 1.03.  The order just isn't that tall, and properly selected parts mean its going to be plenty streetable. 
 

Definitely, all things being equal I would opt for a 5.0 due to the lower cost of running a roller cam.  Case in point, AFR swapped a set of their heads onto an otherwise stock 5.0 and made over 300HP with the stock cam and stock pinched exhaust headers!  Again, EFI, and professionally tuned, BUT a real cam, headers, and other simple 5.0 bolt ons easily could push it to 325 or more.