wheel offset

On an 88-98 fullsize, what offset do I need on a set of 20 x 8 1/2 wheels to fit under the wheel wells with a bodydrop?

14mm worked for me on my 92 chev man..lol montana...i almost moved to columbous..

Hey i have 20x8.5 on my bodydropped fullsize your lugs are 5x5 or 5x127 and for backspaceing you need a 5" backspace or a 6mm offset

i know this because i'm stepping up to 22"s and i went down and got inches to mm reference guide from LES SChwab, and i'm looking at it right now