Best option is to pack it up on the cross slide so that the cylinder and crank positions are on the lathes ctr line. You can then bore the cylinder hole and face off the end of the casting in on setting using a between ctrs boring bar or boring head followed by a fly cutter.
Then swing the casting around 90 degrees, clock the previous surfacet rue then drill and bore the bearing holes with a between ctrs bar.
If you have the height it is a good idea to bolt the casting onto a rectangular piece of steel flat then you have some nice square edges to set true.




If you don't habe the height from the cross slide then you will need to use an angle plate, the steel mounting plate really comes into its own here




