My 73 455 bolted right in to my 64. I used the 64 389 mounts. I maybe mistaken but I thought my 455 had three bolt holes.
For discs I get the Scarebird brackets and use your stock spindles.
http://www.scarebird.com/12802/13701...ession*id*val*
Your 63 allready has the best rear end made.......................