Used material handling company. I found some odd ball depth racking that worked for me fine. It was 42 inches deep (14 ft high) if I recall and used 36" boards to fit in the lips in the beams. They made me a decent price. I later bought some more from them, again odd ball, 26 inches deep, 12 ft high. Use it for storing cases of oil, my jackstands and some other stuff. Again it was odd for them so the price was decent.
I picked up heavy pallets at work that drums of oil came on, the boards on top were various width but about 5/8 thick. One shelf has a bunch of 5/4 deck board cutoffs on it.
Charles