72 Duster 340 ..... Your thoughts ?!

Important things determine value.

Correct matching #s.
Receipts for professional engine, trans, etc... rebuilds.
sheet metal condition.

A friend Russ from New Port Richie, FL. had one just like it. in the late 70s. His was in mint condition and yours doesnt look far from that.Yr/Colors/340.
Is it from Florida?

If it meets the above 3 criteria Id say ... $15k maybe more...wild guess.