1 1/2" is best. I believe I did mine at 2" because I wanted the slight allusion, with the axle slightly forward in the opening, of forward motion. "Going fast while sitting still" I guess you would say?
I am with you on that. It makes my eyes hurt to see the wheels centered in the wheel opening. A pet peeve of mine I guess.
I am thinking that they were originally place in the forward-of-center position to help keep the mud under the fenders. Very few paved roads back when these trucks were new.
