I just got me a pair of 5 rib alluminum bumpers from Briz. They look like the old 40s Desoto Bumpers.
Pretty sharp and with aluminum you never fight rust again, just polish once in a while.
Frank
P.S. they are about $190 each, but probably the last set of bumpers you ever will buy.
http://www.brizbumpers.com/gallery.html