The tranny was likely switched out at some point, or the engine, or who knows. You're talking about a 41 year old engine and transmission here! What is it out of? Are you trying to make good power out of it? Ask the tranny guy what it has for planetaries and drums.

Forged crank torque converters shouldn't be too hard find, just look for an earlier application, like 1969.

Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street