Try some hyguard for trans fluid. Will allow 250 degrees and tighten the converter a few hundred rpms. Which you will need with the lower numeric rear gear as it will add load to the converter and make it stall even higher.
I've been reading up on that stuff. Interesting opinions, for sure. I like the price of that fluid vs Type F. But I sure don't want to risk any premature damage or wear to my fresh rebuild either...