rebuild a torque converter?

Check the converter hub also for any indication of rust and/or indication of groves or wear. The hub must be mirror smooth just like a crank journal or you'll have problems. Seal leaks for sure, and possibiley taking out the pump bushing.

At one time flushing machines were in a lot of transmission shops, but with the advent of the lockup converter, flushing machines became obsolete. No flushing machine could clean out a lockup converter properly and all the shops I called upon when I worked in the industry got rid of them.

I don't think that converter flushing machines are even built any more.