Advice on box reinstallation

[4Ray]

I'm rebuilding a 2003 regular cab 4X4. Frame partially repaired prior to my purchase. Penetrant and heat ineffective. Only way to remove the box was to break the bolts due to the amount of rust. Repairs completed and now its time to reinstall the box. How do I install new flange nuts into the U-channel where the box bolts screw into? Existing nuts are toast. Box is in good shape but I can't drill and tap the exisitng nuts due to the rust. I've thought of drilling a larger hole in the channel and spot welding a nut into position. What have you done that worked for you?
Thanks for the advice.
4Ray

 

[Rock62]

Have you looked at using a Heli-coil insert?

 

[tacojoel]

They have these blind nut fasteners, but you need the tool to install them.

 

[JayQQ97]

do you have pics of what you are up against?

 

[Rock62]

They have these blind nut fasteners, but you need the tool to install them.

I think you are talking about Rivnuts. That would be another option.

 

[4Ray]

Haven't had the time to work on this. In Florida with my wife who is in an intensive physio program and spend the day with her.
Helicoil won't work as the channel metal thickness is too thin. I'm not sure the rivnut option would hold up or if they even come in that large of a size. I'm going to stop at a Toyota dealerhip to see if I can purchase the correct flange nut. I could cut a slot into the channel, position the flange nut and then weld over the slot that I cut into the U channel.

 

[Rock62]

That sounds like a reasonable solution.