The rover drive is a bit of a pain to get right in my experience. i actually fixed one up not long ago. Being that you have had the plates machined (not common to go that far) what is the gap between forward and reverse like? I'm talking the distance the plates move from forward to reverse. Greenfield had a tool that was about 2mm thick you put between the plates to check but from memory rover put a retainer spring in there. should only be a couple of mm between forward engaged and reverse though.
Secondly where is you're pedal adjusted to? 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.
As for Lucero's problem, to do the drive in the late model ranchers the entire rear sub frame needs to be dropped out. There are no manuals on this, apart from parts lists. If you are not comfortable with just ripping in and pulling it all apart I would suggest taking it to a shop.
