[Pops]

Well, here I am again. I was under my '66 the other day and spotted a few holes under the rear of cab floor. I noticed the holes were perfectly positioned for seat belts and come threaded. The middle holes appear to be plates with built in nuts; the outside corner holes appear to be weld nuts. It seems lap belts were an option in 1966 so the holes were put in all???
Anyway, are they safe to use if floor is solid? It looks to be an easy install. I tried to get some info and directions on this forum but came up short. Perhaps I'm not using the "search" correctly.
Is it as simple as using a washer, lock nut, grade 8 bolt, and making sure the metal portion of the belt is flush with floor? Can the belts be anchored without any swivel since they are lap belts? Anyone know bolt sizes, lengths, and thread info?? I have a pair of belts that look well made. I was told they came off a half ton ford though w/o ford logo. I will check tomorrow for fit. Advice needed. Thanks.