I read lots of older threads where folks were looking for a real 51/52 (48-52?) back bumper.

One popped up on e-bay tonight starting at $15 and looking pretty good - no bends or big rust.

I have mine it's at the chrome shop being plated with my next paycheck.

Good Luck!
eBay Motors: 1951 1952 FORD F1 PICKUP TRUCK REAR BUMPER W BRACKETS (item 320258906597 end time Jun-08-08 17:04:48 PDT)