[FWB]

I'm with Dugly on this, FWIW full size 4000 lb cars came with 2.73 or 3.00
if you want to keep the C-6,

I put an AOD in mine, not cheap to make it handle the torque of a big block but wow, what a pleasure to drive. count on 3500.00 plus til your done..

i had a c-6 in mine before, the mount had to be moved slightly and the driveshaft length modified to accommodate the AOD.