Here is an article from Mopar Action that covers factory disc-brake swaps. Best info I've found. http://www.moparaction.com/tech/archive/disc-main.html
The only problem I see with the Disc-o-tek article is that is says do not use the similar 73+B or FMJ spindles.... Which is BS because you can without any issues! People have used these for thier conversions for years without issues... here is a spindle comparison page;
http://www.bigblockdart.com/techpages/spindles.shtml