Gday Troy
I have the engine in the Chassis as we speak. And what Im looking at when I have the engine, and in particular the gearbox, as low as they can go and in an acceptable position front to back are FIVE points that have about 10mm of clearance.
The area where the sump curves over the chassis cross member is the one area that I would consider modifying. Cutting off the corner of the tube and welding in a fillet would help a tiny bit may be 8mm of adjustment in the engine position but that would be enough.
I would prefer not to cut or modify anything. That leads me to an entirely different question. How much does an engine vibrate, that is how much distance dos it move, when it is being used. Maybe I have to put that question in its own post.