Stripped floor bolts/nuts

[PHOENIX]

I dont know if it was me or the presious owner who damage the nuts in my truck but I was wondering if anyone else ever had this problem.

Pretty much every nut welded under the cab for the seat and seat belt bolts are stripped. The front passenger side seat nut weld broke and I had to cut the seat bracket years ago to get the seat out. When I get around to dropping the gas tanks to replace the sending units I will weld in all new nuts and use new bolts.

Last night I was working on getting my interior stuff (amps, carpet, etc.) in after ripping it all out when I did the clutch. I remove the center hump inside, it makes it much easier to work on in the driveway. Well I had some seat belts (lap only) I bought over a year ago that has just been sitting around. I never use my seat belts because the shoulder strap rubs on my neck and drive me crazy. I have tried the little clips that are suppose to help but I dont like those either. So I decided its better to use lap belts then no belts. Well to get the seat belt bolts in I had to drill out the remaining threads in the old welded nuts and use new hardware with a nut on the bottom. The seat belt bolts can all be reached from under the truck. The very outside bolts are on top of the tank, but you can reach up and get them. The seat nuts however are way up there and I dont think I can reach them. I can get the seat in, it just doesnt bolt all the way down. I didnt mess with the seat nuts much last night, I am going to check it again today and see what I can do for now.

Anyway my question is has anyone else had problems with these welded in floor nuts?
The one welded nut just broke and the others are all stripped. I am pretty sure I didnt strip them, but I know I made them worse. I have always had a hard time with the seat bolts, but have only removed the seat belt bolts a time or two before this and had problems with them going in smoothly. The bolts all look fine, its the nuts.
My truck has very little rust and none on the floor boards.......one good thing about AZ, too bad it has to be so damn hot.