[OG68]

BDK did give some good advice. You need to know what you currently have and the PHS is a good start. It will at least tell you what the car came with from the factory. If for example, the 3:08 'economy' axle was ordered that would be a big reason why the car doesn't accelerate well. However, Pontiac engineers wouldn't have offered it as an option, if they felt drivability would be affected.

If you drive primarily in town then a rear axle upgrade may be your best bet.
If you plan to drive to Reno, Salt Lake or SoCal often then stay with what you have.

4 bbl carb and a cam are always nice but thats horsepower that is used primarily at higher RPMs.
A six cylinder gearbox will help but it's designed for a six, not a V8.

So between now and the time your PHS documents arrive, educate yourself on how to check your rear axle ratio and the differences between a Saginaw, Muncie and Dearborn transmissions. They're all good transmissions but were designed for specific applications.