We got our bumper parts for the 1957 Buick back from Keystone in Minnesota we used them back when I did autobody repair under the name Northstar bumper,WOW they did a fabulous job and with the 10% off coupon I got at Back to the 50's they had a very fair price and they gave me prices at their booth. Give them a shot if in the Minnesota area!
even if you are not in MN but have a local Keystone, you can take your bumpers there and they will ship them for you (to and from) on their dime..kind of nice. expect at least a 12 week lead time and yes they do great work when they want to. I used to work for a local Keystone and saw plenty of re-chrome-ables sent back as junk that were sent to Advanced Plating and were chromed when they were returned.