BigD - What about gearing ? My 4 speed + 3.55 + tire combo requires that I shift into 3rd gear to hit 60+ mph. Given all the low end grunt, would it not be better to have a taller rear and only have to do a 1-2 shift to hit 60mph and be easier to launch? (Plus added benefit of lower RPM on the freeway.)
As I see it, higher numerical gear ratios have only one main advantage. Straight line acceleration.
Here: are some of the advantages of lower numerical gear ratios:
(1) Lower highway & cruz rpm.
(2) Better gas mileage.
(3) Should give engine a longer life.
(1) Less acceleration.
(2) Might cause more clutch wear, because of more slippage required for getting the car moving.
SO, for street driven cars, the best gear ratio is a compromise. And, it depends on the driving habits & goals of the driver.
(1) If you do LOTS of high speed freeway driving, then ratios between 2.41 & 3.08 might suit you best.
(2) If you prefer lots of acceleration, & don't really care about fuel mileage, then ratios between 3.55 & 3.90 might be better for you.
(3) So, the compromise gears might be 3.23 to 3.42. I think these were the only 2 options for the '78 W72 4-speed Firebirds.
All this is assuming a 1:1 high gear ratio. An overdrive trans changes things.
Taller or shorter rear tires can also change things, slightly.
4-speed manual trans are available with numerically higher 1st gear ratios, which will work better with numerically lower rear gears. My '69 GTO had a 2.20 1st gear ratio, with 3.90 rear gears. I loved it. But gas was lots cheaper back then. I think the most common 4-speed 1st gear ratios were in the 2.50's & 2.60's. I think 2.88, 2.98 & maybe even 3.08 are available.