I recently pulled my starter out of my Discovery. I had intermittent issues with starting and after eliminating any electrical issues I pulled it. After pulling and inspecting, the metal cap on the Bendix (the part below the toothed gear) looks like a woodchuck had been chewing on it.

I inspected the Flex Plate and didn't see anything wrong there. But clearly the Flex Plate was able to touch and chew up this portion of the starter.

I then bought a rebuilt Bosch starter but I do not want to run into the same issue with my new starter. Clearly there where some clearance issues between the starter Bendix and the Flex Plate. The previous starter was a cheap starter so it could have been that the tolerances where out of spec.

Anyway I wonder if installing some shims would be a good idea or even necessary with this new starter?

 

First don't install shims

Most likely the aftermarket starter you had on there was not to spec.
Simply install your new one and go for a crank !
If there are no clashing noises don't worry!
The engine/ flywheel does not have a tight enough tolerance to affect anything in that area.
T/V