transmission question

[no1uno55]

i bought a 84 swb last year and is my daily driver now.(started life with a 305 th350) in sept.2000 original owner had a new gm crate 350 installed same transmisson. the engine only have 20000 miles on it but it shifts to early. is there a adj. somewhere or a cable or something.what i mean by early is after i take off the first few gears are fine but it will shift into high gear way to early but if i give it a little more gas it will shift back. when its cold it dont do it or when i pull a trailer. the original owner said it has done that since it was new in 1984 and the dealer told him it is the kind of torque coverter it has in it.

also the engine wont rev up real free any ideas?

8 year old 20000 miles on engine, th350, a/c, power stearing, fan, alt., you get the idea. header, duals no cats no cross over pipe turbo muffers (for now)
2 1/4 i think.i have tuned the engine plugs, wires, cap, checked the timing had the carb. cleaned and rebuild. quad-jet. if i just stomp it from a stop it sounds like it is firing to late or something.

thanks in advaced
joe