I have a 1970 GTO which has a non original Pontiac 400 (1972), a non original M20 (1971) transmission and original 3.56 posi rear. The car drives and shifts fine. The car was originally a Auto and was converted years ago to a manual. I don't think the shaft was changed.
My problem is that the PRM get high very quickly in each gear. At 60 mph my RPM's are screaming at over 4000. Any idea where the problem could be?