They usually measure from wheel mount surface to wheel mount surface. Your Nova should be 57.75 so if you add for brakes and hub the 9 inch is 61.25 inches. A lot of that will depend on the wheel you want to run. With it just being 3.5 inches longer you may be able make that up with wheel offset. Still you will have to relocate/ replace the spring perches to match your springs. Just be careful, if you decide to change the gearing and go with a posi dif, you may spend a lot getting everything set up. I had Quick Performance build the exact one I wanted that allowed me to use the disk brakes I already had and was the same width as stock, Just cost around 2K to make it easy.I have a good lead on a ford 9 inch from a 69 f100. seller says it 56 1/2 backing plate to backing plate. what modification do i need to do to fit in my 63.