Use a small bearing 9" and the brackets will still work, your 8" axles will interchange with the 9".
I'd consider using a stronger 67 or later 8" centre with an Eaton Truetrac.
 

Last edited by 50vert (2/22/2022 2:23 AM)

If axles are your concern, then you must convert to 31 spline.  28 spline are same 8” or 9”

The big bearing brake brackets fit both Torino and early style 9” as well as Versailles.

I just bought a Speedway 9” traction lock for my 69.  It is totally quiet!!! And 1/2 the price of the Strange setup in my 66 that makes noise.

I bought my 9" from Quick Performance back in 2013, when I was converting from 6 cyl to 5.0. I haven't had any problems with it, though all I really do is drive around town. Never been to a track, but it's worked great for my purposes. Link is to the site I bought from in case there is more than 1 Quick Performance.
http://www.ebaystores.com/Quick-Performance-Racing

TKOPerformance wrote:

I wouldn't worry to much about the axles.  If they are old my concern would be a fatigue related failure, not a failure from being 28 vs. 31 spline.  We ran 28 spline axles in 8.8s many times without issue.  Traction is what kills them, which you don't have.  Heck, in the GM 7.5" 10 bolt 28 spline axles were an upgrade from the stock 26!  If the axles are old maybe just get a new set of Yukon, Moser, etc. in 28 spline.

Bolted is correct about overall 1st gear ratio.  In a typical V8 that winds to maybe 6,000RPM you definitely don't want to exceed 11:1 and if its only maybe 5,500 stick to 10:1 or 9:1.  Otherwise first is like a granny low in a dump truck.  I used to see guys race Fox bodies with 4.10s and they had to shift almost right out of the hole.  First in the T5 was 3.35:1, so overall they were at 13.7:1!  They'd need 4th at the end of the track and cross the line at some stupid low RPM.  The car would actually run faster with a 3.55 gear.  Better 60', and cross the line at 6,000RPM in 3rd. 
 

28 splines being tough enough is what I was mainly concerned about. With so much 'information' available these days it's sometimes hard to separate the bench racing talk from real experience. I have a line on a 4-pinion 8" Truetrac in an 'extra rib' case that I think I'll pull the trigger on. Axles looked to be in very good shape when I inspected them a few years ago, this car was a single owner job in great shape that I doubt ever got driven hard. Maybe I'll wait and see if anything breaks... I like zipping around more than draggin'.

Fun with numbers - (think these are pretty close)

With a standard T5z gear set and 3.50 rear 1st would be about 10.3:1. Breaking it down with a 25.5" tire:
1st @ 44mph = 5980
2nd @ 66 = 5900
3rd @ 100 = 6180
4th @ 130 = 6000
5th - Cruisin' at 120 = 3490

With a standard T5z gear set and 3.25 rear 1st would be about 9.6:1. Breaking it down with a 25.5" tire:
1st @ 46mph = 5810
2nd @ 72 = 5980
3rd @ 102 = 5850
4th @ 135 = 5780
5th - Cruisin' at 120 = 3240, golden!

Go with the 3.50 gear if you are buying new gears.  That's what I have and its just about perfect. 

I should mention also that I now exclusively use Yukon gears.  Over the years I've tried at least a dozen brands of gears and Yukon remains the best.  Most recently I bought a set of 3.73 Ford Racing gears for the 8.8 in my '89 GT.  What could be better than Ford parts, right?  Something was off with the machining of the splines of the pinion.  The yoke would not go on more than about 1/4".  I tried the old yoke that came off the car, as well as the brand new Ford yoke I was going to use, and both had the same issue.  I sprayed the splines with blue layout die to see where the interference was and it was on every spline.  Basically the splines were too wide.  I bought a set of Yukon gears and both yokes fit like a glove.

The Richmond gears in my '67 whine on deceleration.  I've head this complaint from half a dozen other guys with Richmond gears.  I used a set of Motive gears once that hard a terrible pattern despite the pinion depth and backlash being perfect.  Anything made offshore without proper controls is going to be junk.  You'll chase pinion depth forever, unless you have a pinion depth tool, and even then don't expect a good pattern.

Point being, Yukon gears are a bit on the expensive side, but you really do seem to get what you pay for with gears.  After building a couple dozen rears and having Yukon gears in applications where they now have 50-100k miles on them with zero breakage and zero noise its all I'll use. 

I will say that you may get a better price from Amazon than directly from Randy's Ring & Pinion.