Dropped the 79 Big 10 need backspace help

[Moose62]

Got the 79 big 10 dropped and in need of some 20x9s. Going with a 20x9 and 255/45/20. Not worried about rubbing as I will fab taller inner fenders in the front. Saw another truck with mob steel wheels 20x9 with 4.5" of backspace on all four corners. Anyone else have backspace suggestions for a 20x9 in the front. Basically I want to be able to rotate tires, don't care about offset wheels front to back, rather them be all the same.