Th200-4r
O.K. , I googled this and spent hours reading and taking notes , I think this is the right way to go , now to find the core as there's quite a few different ones to choose from .
Apparently the pre 1988 Model year ones don't need any switches to operate the lockup TC , it's done internally , just apply 12 volts to one pin and you're off & racing .
GM makes a DP , DT brake light switch you run the 12 volts through so as soon as you touch the brakes , the lockup cuts out .