Sounds like you have a dilemna with that one. Is your truck a true 1-ton and not a 3/4 ton?
The 1 tons had a slighty narrower frame. Plus the frame was taller and the kick down section in the front is slightly different. With that being said, swapping in the 6 lug frontend would be a bear. You would either have to drill a half ton axle to fitter the 1-tons wider springs or machine your spindles to fit the 1/2 ton hubs.
You may be able to find bearings to retrofit the 1/2 ton hubs to the 1 ton spindle. Dig through the Timken catalog to find out.
http://catalog.timken.com/app.php?RelId=6.4.7.1&bookcode=trb12
