If the cylinders aren't sleeved down, it would have to be a service block 352, the 4 bolt mount pads weren't until probably the '66 model year and the last for the 352 engine. I have come across many FEs without casting numbers. the date code and bore pretty much indicate it to be a service 352. The one date code with a T at the end and stamped in was likely the original assembly date, also indicating a service built engine/shortblock. It is not unlikely that they were using 390 blocks not bored fully. The .027 overbore would also be what the .030 rebuild size, which would have likely been in a remanufactured engine form Ford. The assembly date code would suggest that it WAS assembled at a Ford plant and the casting date would indicate it was cast 2 years after the 352 left production.
That's not a hairline crack in the
oil pan flange, in the pic by the filter mount, is it??