Nick is a valuable asset to the transmission category of this forum. Lose the attitude and pay attention, you might learn something.
I agree, if the transmission is out on the bench, I wouldn’t pay a dime for a shift kit in a 400. You can do the exact same thing (only better) during an overhaul. And if you’re making big power, the sandwich design transfer plate isn’t the best setup with big power. The tiny channel in the spacer plate can only move so much fluid.
The ONLY parts I’d consider using from a TransGo shift kit during an overhaul is the intermediate clutch snap ring, the pressure regulator spring, and maybe the spring in the low/reverse servo.