Does this sound like a torque converter issue? More?

1972 Dart 318 904, 110,000 miles.

Last year my radiator trans cooler developed a leak and I got coolant in my trans fluid. I put an external cooler to bypass the stock cooler, drained the fluid, changed the filter and new fluid. It seemed fine for about 3000 miles. This week I drove the Dart to work and it was fine in the morning but when I went home that night, as soon as it warmed up, it didn't want to move at the next light in any gear. The engine would rev high like it was slipping, eventually I could feather the gas and it would creep forward a bit. I pushed it off the street and checked the fluid which was fine, got back in and it was normal again till the next stop. I found out if I just shut the engine off for about 30 seconds it would engage again. I limped home the last 6 blocks this way.

Today I checked the fluid again and smelled it, it didn't smell or look burnt. I tested it warm again and did the same thing with a little shuddering and a couple of thumping noises to boot.

Does this sound like a torque converter only issue? I'm thinking that while I have the transmission out I should just go ahead and rebuild it. This is a street cruiser only, stock 318, the only performance upgrade I plan is dual exhaust with better manifolds.

Advice?