Calm down mate, I'm not having a go at anyone.
I'm not saying what's right & what's wrong, but for me personally elongating a hole that much on an engine mount pederstal just seems wrong.
For all the effort to fit the engine, I would spend a little more time to prevent an elongated hole.
The reason I ask about the gearbox output is, moving an inch forward is fine, but then a different diff setup goes in & it sits an inch further back.
Next thing the tailshaft is laying on the road.
Just small things to consider.