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, and a free to me Weber One Touch Silver 18.5" kettle