Mopar 340 HI-PO exhaust manifolds (68-70)

Hi, have an interesting one to think about. I acquired a set of the 340 manifolds that came on A&E body 68-70 that are the more sought-after style. They don't have ANY casing numbers on them and they were pulled off when almost new, to switch for headers on a 1970 duster 340. The 340 they were pulled from is a 1-9-70 and I talked to the original owner who literally almost 'gave' away the engine and manifolds to me. I doubt the casting numbers or dates were ground off. They SHOULD be cast LH - 2863553 and RH - 2863549, but these have nothing. Any ideas??