I'm in the middle of rebuilding the brakes on my '71.. It came from the factory with manual brakes.. I'm replacing rotors, drums, calipers, wheel cylinders, pads, shoes, springs and misc. hardware, etc.. I'm converting to power brakes with the addition of a kit I got from Summit..
https://www.summitracing.com/parts/sum-760197
I had to "massage" the lines going to the proportioning valve but the existing lines will fit.. BTW.. I shopped several sources.. Summit has the best price $159.99 and free shipping.. This beats ALL others by as much as $100..