I understand the attachment to the truck and You should continue doing it then. I would box the frame, get a Dana 60 front end, and a sterling 10.5 rear or dana 80, and fab a four link triangulated suspension using airbags or and adjustable coil over. And if not the same at the rear then use 1 ton spring pack with half the springs removed and supplemented with air bags. That way you have the axle placement and control with the leafs and ride height adjustment with the bags.

But I can tell you that with the current i beams you can not only bend the I beam, but also snap off a spindle toast bearings etc. I had a stock 97 F250 heavy duty with the powerstroke, it had the dana 50 heavy duty twin i beam, and one time i went through a rut and bottomed out on the bump stop. It bent the drivers side I beam so bad they had to replace it, and that one is certainly stronger the a 1/2 ton 2 wheel drive beam.

Anyway you could just drive it until it fails while locating the proper gear for the swap, I just would hate to see you have a wreck over it. Watch out for pot holes.

Here is some encouragement its a f 350 but its a 7th gen anyway.

http://cgi.ebay.com/ebaymotors/1993-...#ht_500wt_1182