Join Date: Jan 2018
Location: Coopersville, MI
Might also check on the intake, heads, exhaust manifolds, carburetor, and accessory drive brackets and pulleys for date codes. If your intake, exhaust manifolds, or heads are proper numbers for your car and the date codes look right they may have blown the original 396 and picked up a 396 short block from a junk yard for an "in-kind" replacement. Engines didn't last 200,000 + miles back in the 60's unless they were the stout 250 Straight six, I swear you couldn't kill those things as long as you kept them in oil.
Back to the TH400 transmission, if it is a floor shift with the correct shift pattern or a column shift with the correct pattern it is a good sign the car had the TH400 origional as the other auto option was a power glide and the shifter detents from it would only allow you to manually shift into P R N 3rd 2nd, you wouldn't have the final detent to allow you to shift into 1st gear.