Ok, I managed to pull apart the gearbox from the old rida cut and this is what i found.

This show the internals with the gearsets, it has 3 gears and reverse.

Good size bearing for the main shaft

Clutch packs need a little work.
Looks like this may be a way to go with the new build once i have rebuilt i will see if it will fit into the chassis.
Cheers
Baz