My stock foot switch self destructed - water+pot metal = oxidation = failure, I was just left with handful of pieces. One of the bolts has broken off and the other is rusted into the captured nut and just spins. Looks like surgery is needed. Question is: Who has done this? I believe that the nuts are captured by sheetmetal retainers that clip into the firewall from the outside and then get covered with undercoating (I haven't done any debreeding yet but recall this from another car, a diagram, can't remember.)
Anybody know the bolt, nut, thread sizes?

I've got 2 used switches, one round, and a second which was described as a factory replacement. I'd like to get into 'em and clean and lube before installation, but it appears that I have to grind away swaged pot metal rivet like closure to do this and am wondering how to put it back together, before I start taking it apart.

Ideas, experience with this operation? thanks