In that case, you want a nice wide tire on a wide rim. I'm running a 12.5" BFG mud tire on a 10 wide rim.
Pizza cutter (narrow) tires only dig down. You have a light rig, use that advantage.
Mine is so light on it's feet I've actually drifted it over my foot with no harm. BUT, I don't recommend that.
I know guys that run 14.5" rubber on 12" wide rims that are even better at floatation, and that's what you want. It's all about pounds per square inch pushing down... think show shoes.
Hardcore rocks may show a weakness in the axles with that much leverage. In the perfect world the back spacing would be about equal.
A fully loaded Ranger is 3000 lbs?
sammy - curb of just over 2000 lbs and payload of almost 1000 lbs
1995 Suzuki Samurai specs, auto safety at Edmunds
If you know someone that is running 14" rims, why no just ask him what they are?
Maybe a utility trailer place?