Hot Rods Ford pickup rear fender bolts

I am working on a 56 Ford pickup and would like to get the old fender bolts out. They seem to be spot welded in and certainly do not come out with hammering. Don't remember this problem when I did a 41 pickup years ago. Any suggestions? Thanks

 

Yes the heads are spot welded to the bed side. Very difficult to remove without causing damage. I'd leave them if you can. Cutting/grinding is about your only option...

 

I've dealt with these before and found out the hard way, after breaking off a few bolts. I didn't want to cut and grind the heads for fear of.....everything. I decided to drill through the heads, chamfer them nice and deep and weld in a stud. That worked around a bunch of work, and came out great.
Another one I worked on, had the same problem with rusted bolts. This time I used a nut splitter instead of taking chances. That worked out even better!

 

After breaking a few on my F-1, I drilled them all out and used stainless button head bolts. Not as handy to mount and dismount the fenders though.

 

Cut off and install elevator bolts. You can tack these in place like the stockers.