i just bought a 79 and the last owner welded the rear end up, the only problem is i use it on my farm to haul feed up and down the road and the steering system keeps coming loose, could the rear end being welded up be cause of the problem and if so how do i fix it.

what part of the steering is comming loose? the rear end does put added stress on the front but shouldn't work anything loose as much as you're describing.

It's sounding like you have a steering problem, not a welded rear axle problem. Put the front end on jack stands, and check things out