[gtnby2]

" drivetrain is a c-6 w/ a 9" rear. "

Here is roughly a 60HP loss....C-6's are a hp hog!!! If you want to make a night and day difference in your car, switch to a C-4 or a built AOD. I tourched my AOD and got a brand new c-6 for 75 bucks so I couldn't pass it up and my car dyno'd @ 157hp with a built 306 after getting the AOD rebuilt, a 2200 stall and NO other mods on the same dyno it went up to 275. Do you have a stall? If you drive the car, a 2400 to 2800 would be ideal, if it's drag only you can go up to 3500 or so. A 408 with your setup should easily be in the upper 300's on HP and over in torque so a stall rated at 2400 would spool up to 2800 easily if you just crammed it but move around town at 2400 or less and act like a stocker.