What backspacing to get?

Ok so just ordered my 3 inch lift from toytec and now im going to get new rims and tires. I already have the rims I want picked out but im confused as to what back spacing I should get. I want to go with 285/75/r16 tires and the rims I am going to get come in 4.0 and 4.5 backspacing. The website says that if I go with the 4.0 backspacing that it will give me more clearance with the UCA's but it will also make my tires stick out further. I realize I will have to trim inside the wheel wells to make the 285's fit without rubbing. Will I be ok with this setup or is there something I am forgetting.

Edited Post

 

anyone??

 

You can fit the 285/75/16's with the 4.5" backspacing with a little trimming. Most folks on here run the 4.5" BS rather than the 4.0".

 

Why do they run the 4.5 instead of the 4.0?

 

4.0 will stick out to much

 

Anyone have pics of their truck with a 3 inch lift and 285's with a 4.5 backspacing.

Edited I had the wrong backspace number up there