Picking up this thread again. I need to go the opposite way of acenho. I have a 68 400 vert, original engine. It was rebuilt at one time, but I know nothing about the internals. PX TH400 trans, rebuilt recently. I believe I have an 8.5 X body rear end. I found these codes on the front of the passenger axle tube. Looks like an early 70s JB code 8.5 with either base 2.73 and up or 3.08 and up gears. The shop I use told me the gears are much taller, in the 3.90 to 4.11 range. Just moving down my street, I'm in 3rd gear before I hit 30 mph.

I do plan on doing a fair amount of driving both around town and on the highway. Once I get into the engine, I plan on doing a mostly stock rebuild with a bit more cam. I'll keep the TH400. I'm looking at a 3.36 or 3.55, but leaning toward the 3.36 with a posi carrier. I will have AC back on the car at some point with 15 x 7 Rally IIs and probably 235 60 tires. Any thoughts or feedback on that combination? Thanks!