My '56 GMC uses two 1/2" bolts with three grade marks and two 3/8" also with three marks. I think the 1/2 " ones are on the front of the floor, the smaller under seat/gas tank. Hope this helps.
Dave
Well, my time went so quickly,
I went lickety-splitly
Out to my ol' 55.
As I pulled away slowly,
Feelin' so holy,
God knows, I was feelin' alive..... Tom Waits, Ol' 55
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