7 1/4 to 8 3/4 brake swap

Why not go with 10" brakes on the back of the 8 3/4????
I will be installing rear discs on my 70 Dart.8 3/4 Which means the backing plates with ebrake cables, complete ,new hardware kit, new shoes, new wheel cylinders. new drums, will be available for sale. It seems you are already in the middle of the swap, These wont be available for at least a month