there is a full 1" difference in diameter from the 60 series to the 65 series.. that will be heavier and change the speed your engine/transmission run at, so youll notice a slight decrease in acceleration and handling.. but your vx will sit 1/2" higher for offroad purposes.. they are about the same size (height) as a 285/60/18 terra grappler than many here have used and loved, so i think you would be ok as far as fitting.. if youre like me though and push your vx through turns hard i think youll be happier with the smaller size,
right now the tires im looking at are..
nitto terra grappler 255/60/18
goodyear fortera tripletred 265/60/18 (this is probably what ill end up with)
goodyear wrangler duratrac (would have to get smaller rims probably but i really like this tire)
bridgestone dueler APT.. not sure about sizing on this one but i do like the tire itself
also considered the falken ZEIX TZ-01 265/60/18 for on-road only
things to look out for when you are buying your tires...
make sure they are at least an S speed rating.. H (this is what came factory) or V would be ideal
generally the larger your voids between tread, the better your weather traction is
directional tires are better for wet handling, but can cause problems if you have a full size spare, and you dont find many truck tires that are directional anyway
if you are calling around for prices.. make sure you make the shop specify whether you are being quoted the tire price or the installed tire price.. theres usually a pretty big difference (20-30 bucks/ tire in most cases)