Hi,
I've got a set of Bilstein 5100's leveling the front. Currently stock otherwise.
I'm looking at some Fuel Pump rims, 18"x9".
I want to go up in tire size to 33" or 34", and currently looking at getting Duratracs.

I've found the rims with 3 different offset/backspacings:
1/5
14/5.5
20/5.75

The tire sizes I'm looking at are 295/65 and 295/70.

Which offset/backspacing would be best, do you think I'd have any rubbing with either, and any other suggestions?
Would the 34s hit the gas mileage/power that much over the 33?

My terrain is sand, mud, and highway for the most part, with ice once or twice a year.

 

With the two tire sizes you chose you should be fine with any of the rims but I would probably stick with the 5.5 backspace since it is the same as most OEM rims.

 

I'd go with a 18x9 with a 5.5 or 5.75 backspace...a 33.5x12 tire would look great and still retain some fuel mileage and performance. They would stick out 1-1/4 to 1-1/2 inches more then stock and give a good stance.

 

I have a 2.5" level kit, running 18X9 wheels with 5.5" of BS and 325/60/18s without any rubbing.

 

I agree with Paw Paw.