I helped my son fix his floor pans on his new 73 Grand Prix, they were not terrible but both had holes, golf ball sized and the back had a few pin to pencil sized. We used the POR with fiberglass, it worked great, then put a little undercoat on the bottom. It's completely sealed now. It cost us less than $200. Instead of $2k or more for new pans.
Great stuff, now the trunk! Fun project for his first car.
Easy to work with. Don't forget your rubber gloves, it has some hang time if you get it on your skin!