Fiberglass body, core-mat reinforced floor , bolting in bucket seats, one 3/8" bolt per corner. Is it necessary to weld tabs/plates to the frame to catch these bolts, or are fender washers on the bottom side sufficient? With buckets this is much more of an ordeal than for a bench.
Same for seat belts - mounting hardware welded to the 1x1 tube body reinforcements, or through bolts in the floor, using their large (2"x3") nut plates?