engine block I.D

[oxo]

Can anyone help on this one?
I bought an engine block on here a while back on the understanding it was an XR2, just been getting around to rebuild it as a spare but the serial number stamped on it is OG110720, when I type this into the merc website it comes up as a seapro/marathon block 3 litre 225hp with a 3.377in bore.
this block only has a 3.155in bore(+.030 oversize) I'm not familiar with the seapro blocks, but this definitely looks like an XR2 block i.e. unpainted with the splodge of green on the top. I just wanna make sure the crank and pistons I have are compatible. Totally confused!

[driver510]

Sounds like a XR2 block. Crank and pistons will fit but centre mains are different, on older vertical reed models they are smaller. If you need any more info call me 07702958175. Thanks Rich

[oxo]

Ok,
Thanks Rich, much appreciated