hey guys i am about to do a lift on my truck with spacer and aal.im going with 37-13.50-20 the wheel i want is the xd seris hoss.well the widest they come is 9 inches.would it be a problem going with a 20x9 wheel for 37 inch tire?

 

No, those will work fine.

 

what would be the best backspacing for this application.

 

Probably 5 or 5.5 inches. 5 inches of bs is the most common.