I picked up a '56 Super 55 Gas this weekend.  The tractor doesn't run, and there was no battery in it.  According to the numbers on the generator compared to my I&amp;T manual, it is a 6V system.  The manual doesn't say anything about it being positive or negative ground.  I didn't realize Oliver had any positive ground systems until I started reading some old posts on here.

Were all 6V positive ground?  If not, how can I tell what mine is?

I plan to stay 6V.  If I want to swap to negative ground, what would be required?