I Have The Beast Running, Driving, 70 Chevelle, Bbc 468, Complete Eagle Forge Rotating, Ls6 Worked Heads,
Problem - Tranny Shifts At 3000 Rmp
Turbo 350 - I Know Should Be At Least A 400 But It Is In There For Now
2800 Stall,
Any Suggestion On How To Change Shift Rpms

 

I haven't messed with old chevys in a while but it could be something as simple as a bad vacuum modulator or a crack in the little rubber hose going onto the modulater making it hold the shift, seemed always to be the problem whenever one of my old camaros had the same symptoms.

You can also get an adjustable modulator and change the pressure it shifts at I believe. Like I said, I got out of old chevy's about 9 years ago.

 

Get one for a Corvette TH350. It's been a long time for GM for me too, but I do remember that one.