new 64 plymouth valiant rear bumper?

If you just need a dollar amount to get an insurance check, you might try Bumper Boyz to see if they have any in stock.

I'm not endorsing them in any way but they are almost always at the major Mopar shows around here. (Mopar Nats for instance) They bring a truck load of re-chromed Mopar bumpers and some people even bring cores with them and trade them in on the spot.