some answers and a web site for you. Hope it helps.
Code Description
JH23 J = Dodge Challenger
H = High
23 = 2 Door Hardtop
G3B G = 318 150HP(net) or 170HP(net) 1-2BBL 8 CYL
3 = 1973
B = Dodge Main, Hamtramck, MI, USA
344812 Sequence Number '344812'
Go to this site and put in the vin than it will ask for the fender code numbers. Once you put those in you will find the options that came on the car.
http://www.stockmopar.com/mopar-fender-tag-decoder.php
Price sounds right but would need to see the car. Any pictures? What options?