The correct trim ring for a 14x7 steel wheel is slightly over 15 1/4" in diameter and 2 5/8" deep. (I laid the ring on the table face down and measured up to the inside edge. The trim rings should have a white sticker on the inside with the engineering number and date stamped on it.
Should be:
D0ZA-1210-B for cars built prior to about February 1970, D0ZA-1210-E after that. ( Valve stem hole changes shape, later hole is oval, earlier hole is more teardrop or football shaped.)
Some people feel that the oval hole rings/caps are 1971 (or service replacements), but I have a set of new car take offs with the later holes that are dated 3/31/70.....
Hope this helps, John