Noah's Ark? 1973 Duster leaking rain water in passenger floor

My guess is clogged cowl drains. If you rinse all the crap out of those cowl drains you'll need to rinse it out again behind the dog leg section of the fender. One advantage of not having a rocker molding is being able to remove 2 fender bolts underneath and pull the dog leg out a bit to clear debris. Watch for fender shims falling out and put them back where they came from.