Gas Cap
'72 & later is internally different from the prior years .
By 1972 , all MoPars had vapour canisters , and thusly different fuel tank vents .
The cap you're describing sounds like a '70-'71 cap , a '67-'69 cap , or even a c.'63-'66 cap .
IMO , you're dollars ahead by purchasing a 'generic' replacement , removing its screwed-on handle , tossing that irritating warning tag in the dumpster , laying down a coat of etching primer ( except on the plastic handle ! use regular primer here ! ) , painting the cap body colour , reassembling and then ---- >:burnout: