Save yourself some headache and run a 5spd clutch combo or a Bruno Liberty 4spd. This will get you in the power range to make the car go. Can't tune clutches, torque converters, and suspension to work with 500 lbs of torque when you are out of the RPM range to 800lbs of torque when you are in.

I saw similar issues with my screamer small block with the powerglide.

Leon