what do i have here

Yes, early 340s (pre '70) had the timing marks on the PS. Very early ones had a metal timing tab, then went to cast in marks on the timing cover before switching to DS timing marks in '70. Not marine, that's an A body oil pan. Casting date would indicate a '69 MY engine, so if no VIN is found, it could have possibly been a warranty block...? Lack of a harmonic balancer is a poser, though...

Edit: I shouldn't say NOT marine, who knows? But marine LAs that I have seen had square pans...