Wow, this one's gonna be harder than hell. Can you describe it? Is it bigger than a breadbox? My WAG, though, is '54 Hudson Hornet Hollywood hardtop.
They are on my 55 and I never took much notice of the 56 cap, thought they were the same as the 55 ones. Thanks again.
'56 requires specific wheels to work, see how far they drop in the back? Need 1956 Caddy wheels, some say they will fit later years up to 64 or so... but the wheels look like they are reversed on the center... just FYI, I have a set on the shelf I can't use at the moment too. edit... just saw you posted they are already mounted on your car... right on.