This post is to help others in deciding what size to run. I drive on the highway and offroad so didn't want to kill the mileage or power. I used Fuel wheels 15x8 with 3.75 back space and 235/75/15 Federal Couragia MT tires. As of now there is no lift and zero rub anywhere with nothing trimmed. I have a 2" lift but think I'm jus going to raise the front a little to match the back.  Also these tires are light and semi aggressive with only slight noise on the highway. Didn't notice much difference in power and 5th gear is still as normal.  Very happy with this combo.

Have you stuffed the suspension when off road driving yet?  Did the rear tires get into the fenders?

I love those tires had them on my 2002 with 2" bl and 2" suspension in the 30x9.5x15 they are so awesome that I would put them back on in a heart beat. In the mud they just throw the mud everywhere, never goyt stuck with them highly recommend

Mostly flat ground here in Florida but have been through  a few ditches and rode all over the forest with Sandy rutted roads with zero rub.

Would a 15x8 with 4in backspacing stick the tires in towards the frame more?

I want to run 31x10.5r15 on a stock sidekick wheel. If that wont work I'll have to look into 15x7 or 15x8. 3.75" is hard to find for backspacing I can get 3.5 or 4" rn all 5 for 240shipped.

Would a 15x8 with 4in backspacing stick the tires in towards the frame more?

More than what?  The stock rims or the 15x8 with 3.75" backspacing that the original poster talks about?

Backspacing is the distance between the back (or inner edge) of the rim to the hub mounting surface, so yes, a rim with 4" backspacing will sit 0.25" further in than one with 3.75" backspacing.  The OEM rims supposedly have a 4.25" backspace, so those would sit 0.25" further out.