That looks like a nasty breakout with fairly large fracture area and thin section.
It should still be repairable.
Accuracy of the repair result will be critical given the thin section breakout, re face of mounting lug to frame and not wanting to stress the repair zone by a mismatch of the clamping faces at the mount.
Using the frame as a jig is one way to ensure maximized accuracy.
The engine needs to be apart, so how about stripping it bare, and fitting an "empty" engine to the frame for the repair?
As in torqued upper and lower casing halves plus head.
Or go Pvester's suggested route.