I made mine by taking a 4x4 and cutting 1-1/2" slices from it. Then drilled bolt holes (3/8" I think) through and then soaked in polyurethane for a day. As long as they are all the same, the thickness isn't critical.

'69 1/2T stepside, Sea Foam Green, 250 L6 w/ 3 on the tree, not an option on it, in the family since new.