need help to fig out value of a 1972 duster

IF it is a 340 car the vin 5th digit will have an H. also it will be cast on the side of the block 2780930 340-x x= cast revision number, also the build date of the block is stamped on the left front side of block just under the cyl head. if it is original on the pan rail it will have a last 8 of vin stamped in it.

concerning is the fact that the owner doesn't know? ugh

if all good there? WIW what someone is willing to pay for it.