8 3/4 B to A swap

I figure I should put out more information before I drop $200 on something that wont work.

The car is a '74 dart hardtop with a /6, 904 and a 7-1/4 rear. I'm planning on a mildly built 318, 904, and a 8-1/4 or 8-3/4 rear, with original 14" steel wheels, I'm not sure on the width yet. I'm hoping to use the driveshaft I have, but if I need a new one, I can buy that at the same time as the rear.

What are the differences between the parking brake cables, if any? Will the minor difference in the rear ends spring perch cause problems down the road? I'm going to be using 14" steel wheels shod with 215-70-14 tiger paws, Is this tire size fine? I haven't bought the tires yet.