I recently purchased a 77' Camino SS.
It has a stock 3 speed and stock rear end.
The engine was recently built and the tranny was rebuilt.. Less than 2,000 miles on both.(hooker headers, weiland intake, Edelbrock carb)
I was wondering what I could do to get some more power out of the car, Is the transmission or rear end .. wasting the engines power on the bottom end/torque.. it will spin the tires very easily in 1st gear with a lil persuasion of the gas pedal and it will cruise at about 45-50 arround engine idle..
any help would be greatly appreciated

My guess is that you have a low ratio rear end. I'd say probably a 2.73 or maybe a 3.08:1. Buy a set of gears for it. Get some 3.73 if you stick with the 350 Thm.

If it feels like its coming off really well in 1st then it just dies out in 2nd its probably the gears in the rear. If you know you've already got 3.73:1 then possibly its something else. Its a heavy truck also so some added torque would also help. Maybe a new Cam or even changing up to a 6" rod or both, stroke it, lots of stuff will give up some more power.