Needs to be pointed out here that Mopar transmissiions were built to9 the original engine's torque output. So a 318 trans is the weakest of all transmissions that would be built in that case. Transman should enlighten us how to get that trans to a higher torque level.
It's similar with 904s with the 318 getting the 998 and the 360 getting the 999.

I became aware of this when I bought a "bulletproof" rebuilt motorhome transmission only to find out it was a 2-barrel 383 tranny dressed as the MH transmission. I didn't know about the ID numbers until later, to my chagrin.

R