I have two racks in mine. I didn't want to make notch in the top of the barrel even tho it would be easier to place it and remove it. So I measured the spit rod and made my holes 1/8" larger, 3" down from top of barrel. Took a few minutes to make sure the rod was dead center of holes before mounting the brackets that hold it in place. May not be the best way but I didn't want to notch it and mess with the lid sealing.
My arsenal, Stumps Clone, Two Modified offsets, open pit with grate and rotisserie,UDS, Weber One Touch Silver 18.5" kettle, Chargriller Pellet Grill, 36" Blackstone Griddle