54 panel,

Check out the tons o' fun page. At the top there is a posted message about 36xx and 38xx axle swaps. lots of good info, mostly pertaining to trucks, but I 'm sure the panel info would be much similar. you have to be picky, but a current 14 bolt corporate axle will fit, and get you the disc brakes.

https://www.stovebolt.com/ubbthread.../14-bolt-axle-swap-info.html#Post1249600

good luck
Jon