Slant 6 engine stamping help.

Yes, mine looks like that and appears to have 3 plugs. I thought that it was unlikely that it was changed, all the hardware was original. I just replaced the original PCV valve last week. It lost the rear main seal and the oil light wasn't hooked up from the previous owner painting it. I ran it a long way with no oil, it blew up but still runs. I was hoping to find an engine first so I could keep it together to move in and out of the garage until I'm ready to change it. Guess Ill probably have to abandon that at just pull the trans and find out.