I just bought a 1996 short bed with a bad fuel sender. I started to pull the bed to replace the sender.

I soaked and heated the first bolt - I used my impact on it. The the bolt broke loose but only spins in the frame channel.

I can't get a wrench or bar in there to stop the spinning.

How is this assembly manufactured? Are the nuts welded to the inside of the channel?

If I grind the bolts off and remove the bed - will I have access to the nuts to reweld them?

How do I remove the bed with spinning bolts?