Captive nut,cage nut,tee-nut,floating nut,retainer weld nut and they are spot welded in place.

Ray Stanley sells them with his body panels.
They look like this retainer nut and are 5/16" - 18 thread size and 2" long base.

Ray Stanley
Wheelwright Restorations
92 Pine Street
Wheelwright, MA 01904
1-413-477-6467

Tim

1951 3100 Chevrolet
1951 Chevrolet Suburban Carryall
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