Couple Observations:
1) Center Keystone Water Port: Is shaped differently than any block I've seen in the USA - has a radius in the lower portion.
2) Lower Keystone Water Port: Is also shaped differently than any block I've seen in the USA - has a radius in the top portion.
3) I've never seen a crank in the USA with 2.4" mains - nor the bearings that go with it.
4) My guess is that the block could use a standard 2.5" main USA crank with associated bearings.
5) There are two strange holes on the bottom pan-rail - one by the oil pump and one up front - about 1/2" or so diameter
6) I have no idea as to what those 4 holes (with the arrows on them) are all about on the intake manifold surface.
If it is a 3 3/16 bore, then it sure seems like a "Mercury Style" block, though it has some obvious cosmetic differences between it and USA made pre-war Merc blocks or WWII industrial production blocks (which are almost like a 41-42 Mercury).
Hopefully it is a good block . . . then I'd channel some of my inner Finn Sisu and put a stroker crank in it, bore it to 3 5/16 and have some fun!
PS: I'm 1/2 Finn.
