RE: crankcase bearings 2510
If it was gas, a 620D motor, there was a bushing on the cranshaft originally on the drive side and the flywheel side only had a machined cover. With proper oil pressure the flywheel side shouldn't have given any problems. Dirty oil will also lead to failure of this kind. I don't believe that after machining the relief for a proper ball bearing, you will have sufficient metal left to avoid catastrophic engine failure if the cover cracks and the bearing drops down outof place at 3600 RPM.
My 2 cents