"Have" it rebuilt?? You gotta be kidding. It's easier to redo the front drums than to install a shift kit; by FAR. See, I'm not saying a complete disassembly..just the two front drums; where 95% of a 904 problems always are.
I did redo the front and rear drums, that’s part of what I usually do when I have a tranny out of the car -
I even air tested everything as I was going through it out of the car.