When you spoke to Howard’s, did you give them all of this information?
Especially the GT40P heads.
Pretty sure springs will require upgrade from stock.

The last set of numbers for some cams refer to LSA or various kits such as cam, cam/lifters, cam/lifters/intake, etc.
That’s been my observation.

I know Edelbrock’s Performer series camshafts for 289 and 390 idle smooth and have vacuum for power brakes and transmission (modulator).

289 (.030) was in my Mustang.
390 is in my friend’s 64 Thunderbird and he tows a small boat.
He drives like an old guy…I mean responsibly. 😁

I would not second guess a cam company's recommendation.  Howards has a great reputation I'm sure they'll do right by you.

As far as performance and economy, those two play just fine.  What I've noticed is that when I increase a vehicle's performance I almost always end up getting better gas mileage.  I've made the engine's job easier.  I don't drive a vehicle any differently respective of its level of performance, so what I've concluded is that a higher performance level uses more fuel on acceleration, etc., BUT I spend considerably less time on the accelerator.  At cruising RPM its probably more efficient than it was once restriction has been removed from the exhaust, etc.  I've always ascribed to the understanding that an engine is just an air pump.  So long as I'm not physically changing the size of the pump, and so long as I don't use artificial aspiration (nitrous, blower, etc.); all I'm really doing is improving efficiency.  That should improve both performance and economy. 
 

Raymond_B wrote:

TKOPerformance wrote:

 I don't drive a vehicle any differently respective of its level of performance 

What the heck is wrong with you! 
 

LOL
 

What the HECK did I tell ya?!!!
108 LSA  = snotty idle.
They recommended  more lift and less duration than me.
My "idea" was less lift would be easier on the springs/valve train.

IF you plan on a 331 stroker then their recommendations is rather mild IMO.
(Which is fine because you will be severely traction compromised anyway with that kind of engine in a 65/66 Mustang.)
Just for $hitz & giggles call  Delta Cams and Comp Cams and get their input (and prices) IF their numbers are close to Howards then you know you're on the right track!!
Roll-On BILLY
6sal6

224-224 duration on a 110LSA..........in a 289!!!!!  Bet that puppy is snotty!!!

Makes MY argument all along.
Just because it stutters..... "like a 14 year old on his first date".... doesn't mean its a hand full around town! 
OLD-OLD Tech HiPo 289's with solid lifters.......327/365HP Shivel-lays....and others were driven on the street back-in-the-day.
Today you really CAN have your cake and eat it too!  Modern roller cams with stupid duration and LSA numbers are very streetable (unless you're a girl!) Manual trannys makes it even easier.
IMHO! (of course)
Cam'um up fellas......you don't live fer ever!!!
6sal6

The world is your oyster if you don’t have vacuum assisted brakes or factory speed density efi.

MS wrote:

BILLY WALTON from GEORGIA wrote:

Ron68 wrote:

Honestly Billy, how much more noise do you need with series 40  Flowmasters? Some cop might stop you and give you a ticket for excessive noise!

It dont really seem loud to me has a nice rumble to it.
 

Changing the two barrel carb to a four barrel is going to change the sound of your exhaust. A lumpy cam will really add to that noise. More compression will add to that. So, you really won’t know the final sound until the new engine is in there. Ifbyou like it, then it is perfect.

I can always head over to the muffler shop and get some quite mufflers maybe some 50 series....we shall see.