disc brake/ 14 inch wheel combo possible ???

I would find some "5.5 inch" J rims, but yes certainly they came that way with SBP disc brakes. Find someone selling a Kelsey Hayes disc brake conversion they are SBP and run 2-300 as a core set.

Here is a conv for sale.
http://www.forabodiesonly.com/mopar/showthread.php?t=257009