drum to disc O.E issue

OK,
All you really need to do is find a '73 up a body with Disc Brakes and get the parts from it.
Then you will only be changing Spindles once. This will take you to big bolt patern but new Rims will be cheaper then the alternatives. << My opinion only!
Give this thread a read through:
http://www.forabodiesonly.com/mopar/showthread.php?t=90216

Hope this helps,
Laer,
Bruce B.