WHat is the difference between the 2800 and 3200 springs for an A-body and how do You know which ones to get? Also if the car will see some street time how will these ride and how much will it raise the back of the car compaired to stock springs.

Weigh the car.If impractical, weigh a buddies with same stuff (drivetrain).
IMHO unless you do a serious amount of dieting (read "hacking") on your car, it will NOT weigh #2800.
The weight of the car is very important when selecting SS springs as the ride height as well as the rear suspension characteristics will possibly be affected adversely.My .02

so if the car weighs 2800 or less you should use the 2800 spring and if it weighs over 2800 you should use the 3200 spring? Is that correct? I can weigh the car on a truck scale that is down the road.

these are pretty harsh if you drive on the street alot.i would go with espo unless you race it often

IIRC the SS springs have "softer" rates than some of the HD springs so they "give" and react in a controlled manner.A lot of it was built in the shorter stiffer front section not allowing the axle as much windup. Yes around 2800 is OK for that rating (give or take a little) If it is closer to 3000-3200 use the higher LB rating.
Again, I am no expert and have not used espo springs.
FWIW I have some severe wheelhop issues with my street tired 440 sixpack 4 speed e body (HD springs /pinion snubber)Is Ok with the snubber, but when I take the snubber off all hell breaks loose.Am considering Cal-Tracs as the best solution but even calvert has his own springs...

what about the springs that mancini racing sells for a bodys. Would this be a good alternative to the super stock springs.