I have an engine that I bought from a friend and he had no idea what year it was just that it was out of a mustang gt (86-89). I found an engine date code but I don't know how to decode it and it is faded. The correct code is one of these three. PK394824, PKR94824, PKB94824. I am also unsure if the 9 is really a nine because it is also faded like the second one. Again this is stamped on the engine on a flat area on the top back of the engine block. Help would be greatly appreciated.