ClassicCar

there are a couple of options, you can buy ready made kits between $800.00 and $1,600.00 several places on the internet. this is the easiest and most expensive both in the short term and long term maintenance because you will normaly have to buy all future brake pads and hardware from the company who provided them to you.

If you are wanting a less expensive alternative you can use the disc brakes on later model chevy trucks (2 wheel drive) they are six lug and you can make sure the spindles match by matching the inner and outer bearings. this does require the fabrication of a bracket to hold the caliper, if you don't have a plasma cutter you should be able to find someone close by who can make it for you. this is the least expensive in the short and long run, the initial parts can be found at local auto parts stores and generally are in stock, rotors are about $35 ea and calipers and pads are about the same the bracket will depend on who makes it, but parts will be readily available and local

the last option is a full suspension upgrade like a fat boy subframe it will change everything including the funky hydrolic units the 48's use for shocks. I hope this helps