Your best bet is to find a GM 14 bolt full float rearend from a Cab/Chassis or box van. You'll want to look for one that has a 63" Wheel mounting surface. There's been several guys use the 67" 14 bolt without clearance issues. It just moves your wheels really far out and super close to the fenders. Dodge vans with the Dana 60 are something you can look for, but extremely hard to find. Most likely, you'll find a Semi-float 9.25" Chrysler axle. Ford trucks with the Sterling axle, and Ford vans with the Sterling axle are also possibilities. Any late model rearend, is going to require some fabrication work, so ultimately it's up to you on what you want to do.
I have a 67" 14 bolt that I'm going to use dually hubs on. If you want to use oem style drum brakes, it creates clearance issues. Since I'm going to disc brakes, it's not a big deal.
Check out my pics at;
www.photobucket.com/whitedog76picsFor some good 14 bolt information go to;
www.pirate4x4.com/tech/billavista/14b_bible/index.html
