Trying to identify. A transmission

I bought a used slant six 225 and transmission, I'm trying to replace the rear seal on the transmission but I'm not sure the year and make on the transmission . The only number I can find on it is. Pk3681841 4639 9219 the auto part store says that doesn't help and wants a VIN but that is the only number I can find anywhere on it .

The part # 3681841 identifies it as a 1974..... 198/225......904..........standard(w/aluminum carrier) tranny. "Standard" just IDs it as not export, police, taxi, truck or high performance.