Yes I'd just make the shims the same size as the whole side of the bearing.
I probably wouldn't buy a shim steel sheet if it was just for this job ,you could cut the side off a paint spray can
to make a shim as long as you deburr the shim after it's made.
Stainless steel would be a better shim ,you could make one from a Stainless Steel Food Storage Container etc.
A few shims made from a coke can would be better than none.
The Rover Drive system has been covered a few times on this site ,but only odd bits of info.
"Unlike greenfield rover decided they needed a spring return to neutral on the pedal. This can get out of adjustment to the drive neutral position limiting the pedal travel and therefore the pressure it can put on the clutch."
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/65001/rover-rancher-drive-system.html
Cheers
Max.
