Hi Doug !
I know your is the B-pillar , both styles very beautiful , still both based on the larger Fleetwood wheelbase .
Another funny thing on this is that it was based on the 1948 Cadillac Fleetwood and possibly therefor got the lower smoother 1948 Cadillac trunklid even if they built the prototype as a 1949 with the overhead 331 motor and grill and dash ………..
Wolf