Tire size upgrade

[jaybirdjtski]

I have a really nice 99 XE 4 x 4 but the tires make it look lame. They're 235/70 x 15. The wheels are the optional lace alloy. The wheel size is 6-1/2 I think anyway.
Not 100% certain. I want to bump the tire size up but I am not sure if I'll need new wheels or not. The local tire shop wasn't any help. He just suggested keeping the same size although I told him the SE version was probably only a upgrade of the same vehicle. I do know the bolt pattern is the same.

Any suggestions as to tire size? Potential problems? Do I need wider wheels? 7's? Any rubbing? Can I go to 265/70 x 15 which I guess was standard for the SE.
What about 16" tires with new rims? I live in the mountains and do go on dirt occasionally and definitely in snow so I'm' leaning toward AT style.

Thanks in advance for any help. This is my first posting here.