It's not any of these two, is it?

http://www.imcdb.org/vehicle_113191-Pontiac-Chieftain-1949.html

http://www.imcdb.org/vehicle_115204-Pontiac-Chieftain-1952.html

Anyway if the car happens to be listed it'll be easier for you to look for it, since you know how it looks in person, here you have the entire list of Pontiac Chieftains listed on the site, have a look at it http://www.imcdb.org/vehicles.php?make=&model=chieftain&page=1