So, I may have been frying those modules because my dwell settings were incorrect. I got the replacement module (Besslers again) and got it installed, and everything is humming along. I set the dwell to fixed, 7ms cranking and 4ms running. I also kept the heatsink attached. In order to fix it for the long term, I went back to Glen’s Garage and ordered up a transistor kit that will take the place of the 4g63 module.
For now, though, I’m going to enjoy having fire on all four plugs. The only question/problem that I’ve got now is how the tune needs to be changed.