I've got a 75 D100 Long bed, and I can't seem to get the bed off of it. I've removed the 4 bolts on each side, but it still doesn't want to budge. It looks like the bed may have been welded onto the frame, but its hard to tell with all the rust there is and I was also thinking that all the rust may have basically fused the frame and the bed together and that could cause it to not move, but I'm not sure. Any of y'all have tips to try to get the bed off? Here's a video showing the frame and bed with a bit more details:

 

Look at the bumper brackets sometimes they are welded on and I've seen the box get welded by them.
But I think it would be unusual for the box to be welded on.

 

Turns out it was just one of the previous owners that decided it was a good idea to weld the bed supports to the frame. I just cut the welds with a grinder and the bed came loose easily