4"x3"x3/16" makes a good base start for sliders if you don't have access I a break. I used 3x3 on mine but didn't add any sort of tube step to it I have stirrups on my jeep. I based mine off if the ones Brook's custom concepts sells
American born and bred, union 'til I die!
United Association Plumbers and Pipefitters Local 430
PM me if you need a diagram I have All Data Pro access.