20 inch wheel offset?

[monstercart]

I am putting 20x8.5 Ridler 695 wheels on my 85 c10. What offset should I use? I don't want them sticking in or out too far. Also doing a 3 front 4 rear drop. Any help at all is really appreciated. THANK YOU.

[Captkaos]

It has been a while but for 8.5" you will be ok with 4-5"  Factory 8" wheels had 4" backspacing.  question is how tall/wide a tire?  Front is a restriction, rear is not.