Ok here are the basics you need to know about RXV revisions, there are fundamentally 2 of them, the 2008-about 2011 RXV's like mine use a Danaher controller system, then in about 2012 They switched to a Curtis brand controller. There were several minor changes that happened between 2008-2010, which only matter if you are considering these early production units. There has not been much change since the Curtis controller units came out around 2012, unless you are talking bout the Lithium battery powered elite model, or other upper end offerings..
The standard RXV is powered by 4 12V batteries, it is possible to replace the battery tray with one that fits 6 8V batteries for improved range. I think this tray costs around $225 online, at least that is what I recall.
If adding a rear seat to a cart that did not have the factory rear seat option you may want to also install the HD rear leaf springs.
Also don't go too big on tire size for the RXV I am running these cheap 20 inch tires on my RXV
https://www.surpluscenter.com/Wheels...s-1-5021-2.axd which is about the largest that will fit without a lift kit (though a 1/4 inch wheel spacer is needed on the rear? to prevent rubbing). With them and a maxed speed limiter (I think standard speed is locked to 8 or 11 mph, and unlocked on stock tires is 1
RXV I get 23 mph, and with the RXV's car like front suspension I would not feel safe going much faster. (Driving an RXV at 23 mph is sort of like driving a car at 80 mph)