54 obviously means 1954, any 20 means Pontiac in this case 28 means Starchief and 67 always means convertable. Hope someone with a list can help you with the rest.
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Happy hobbying from Reid Pearce
"New Series Big Six" 6-30
Pontiac Custom Sedan "Tinindian"
Assembled on June 6, 1930 in
Regina, Saskatchewan, Canada