[Steve Barcak]

Yes, Replacing your stock 2.50 (2.48) first gear in your trans with a 2.75 (or even a 3.0 as I have in my '72 GTO 455HO) gives you much more acceleration even with a heavy car and mild hiway gears. The low planetary gear sets also have a 1.60 second too.
You can compare your advantage by some simple arithmetic. Multiply your first gear in your trans by your rear gear ratio. then do it again with the low first gear to compare. My '72 GTO runs a 2.56 12 bolt POSI and a 3 to 1 low first gear instead of the standard 2.50. My car accelerates like it has 3.73 gears until I click into drive and I am back to 2.56s for high speed cruising, less engine noise and wear and better mileage which equates to a longer range. Since Pontiacs have broader torque curves than most engines, the wider gear spreads with the low planetaries do not have a disadvantage as they might would with a sbc as an example. I use a bigger gas tank too.
These gear sets are great esp for heavy cars with mild gearing and with mild to med power. They cost less than a 77r4 and you still keep the strength of a 400 thm. I have broken a few of them too but, ,mainly in heavier towing applications. I don't recommend or use them anymore to tow anything heavier than, say, a 19 foot boat. They are great for street and street/strip.
Les- "skunkworks?" he he I like it!
Steve