There are a few different options out there. Some guys will tell you to do a 1/2 ton drivetrain swap, while others will say go with the MII frontend, late model rearend. I'll tell you what I'm doing.
On my '54 3600 I've obtained some front rotors and calipers from an '07 Chevy 2500 van. The rotors slide right over the the original hub. The caliper fits and clears everything, I just need to finish making the mounting brackets for it. I'll need to plumb everything and get an updated master cylinder too. BTW- I purchased some roller bearings (not ball bearings) for the front, and I have Ford van rims. The rotor and caliper won't fit in oem rims and some later model rims.
Onto the rear; If you can find a 60-72 3/4 ton center section, you may be able to get a 4.10 or 3.90 gear, but alas they are HARD to come by. Like other posters have stated, Dodge and Ford vans have a narrower rearend option, along with the Ford trucks with the Sterling rearend (Not Dana). Chevy has a 63" WMS (wheel mounting surface) 14 bolt rearend that they used in Cab and Chassis applications that is fairly easy to come by. You can get gears all the way up to 3.42. I just recenty purchased one and plan on using it. You can find some posts made by myself and Grigg in the Ton's O Fun section.
Go to
www.photobucket.com/whitedog76pics , if you want to see some of my progress on what I'm working on. I'm planning on updating the pictures too, so keep checking back.
