Seems like a whole bunch of parts scrounging and mix-matching when you could just replace and reinforce the wheel cylinders on what you have. Bigger drum brakes and more effective drum brakes are the same as far as I'm concerned. The issue with over braking the front/rear bias remains. OP, have you upgraded the fronts or, are you just throwing a bigger anchor off the stern?
Oh, well, have fun with that!
Oh, well, have fun with that!