I figured I'd buy from a FABO sponsor, so I called...

Tri-City offers 63-76 Dart bumpers front and rear re-chromed for $355 each if you send in a core, or $445 each with no core. Sometimes they have the cores or already plated bumpers ready to roll in stock, and sometimes you need to send in yours for re-chroming.
Bumper Cores & Price List – Tri-City Plating Co. Inc.



That's the way I would go. The bumpers on my 68 were about $800 with the shipping