According to the factory brocure,the interior decor package for a 70 Duster would include:
Simulated woodgrain intrument panel (standard on Duster 340 according to brocure but maybe not accurate as some I've seen don't have the woodgrain trim)
Simulated woodgrain door trim panels.
3 spoke steering wheel with styled pad
Rear armrests with ash trays except on Valiant sedan.
However,my 70 Duster 340 has the A62 code on the fender tag and does'nt have any of those so I'm going to say that code on a 70 340 Duster is just for the rallye cluster.
I believe the V8X is for a black tail panel stripe beetween the taillights and the V6X is for a black longitudal stripe that runs front to back on most 70 340 Dusters.
Adam is right,it sounds like you're looking at a real 340 car.