I have a muncie main trans case and I'm trying to figure out what vehicle it may have come out of or at least narrow it down to a few , it has a partial vin # 6S103700, a date code of P1018, and a casting number of 3885010. So far I think it was built on 10-18-66 in ST. Louis, MO. SO my question if what I have so far is correct, is what vehicles did GM produce in ST. LOUIS in 1966 ?