I would save the floor, especially if it's only got a few pin holes, as Barry said, that's easy to deal with as long as you blast away ALL of the rust first. I don't like POR15, I'd either use small welds to fill and grind the holes flush or splice in small patch panels with butt welds. Regular metal prep and a good epoxy primer should do a fine job of preventing future rust until you are dead and buried if you do it right and avoid driving the thing in the snow and salt.

IMO original metal is ALWAYS better than replacement metal, getting the spot welds removed and replaced around the rocker areas is near impossible to replicate when replacing floor pans. Yes, it gets covered, etc. but it's still there. Reproduction metal has it's place, but IMO only when absalutely required as a last resort.