Floor board rust repair?

The floor boards on both driver and passenger sides are quite rusty with several small pin hole size holes. Otherwise they seem fairly solid. I understand some owners fiberglass the floorboards instead of welding in new ones. I was like to know how to prepare the surface, and what size (thickness) of fiberglass and what kind of resin. All of the information on various websites seem to centered on boat or surfboard repair. Any ideas anyone? thanks

Floor boards ARE boards. You don't weld in ply wood. Show pictures of what you have. Your DPO did something fishy.

My mistake--sorry--I didn't notice that I was on the wrong forum--I post things on MGA, Midget, and TR6--Plus I have a Nash Metropolitan, Morris Minor, and Austin--MY BAD