A833 shifter plate removal.

The degree on the heads and the plate make for a high resistance and it’s tough to break them loose with no corrosion involved. I find it easier to use a 5/16 drill bit and drill the center and the head will break off. After that the remainder of the bolt will almost screw out by hand it’s the surface area of the head not the threads that’s making them difficult.
If you can’t get a right angle drill in there your gonna need a good impact wrench and Allen socket to break them loose.