Mogman - I too live in steep country PA. I added the lift kit and went with bigger tires. At first, I kind of regretted it since it raises the center-of-gravity and increases your pucker factor on slopes. I got used to it (complacent?) but just drive a bit slower and more carefully.
If you want tractor tires, a simple option may be to check with the Kubota dealer. As I recall, their BX tractor series rear tires fit on the RTV. Same bolt pattern and everything. If you do go this route, see if they have some "take off's" laying around the shop as that's the cheapest option. If not, order them through the sales department as "whole goods". That option is normally cheaper than ordering from the parts department.