Sorry, all my pictures are old school film type. Van's carries an item called C-606 Link. I will double check the p/n tomorrow when I am at the hanger...
It is a steel link, about 2 inches long, and has a #12 hole in each end. I think my initial one came with a wiring kit, and is used to attach the starter electrical cable to one of the sump bolts. I liked the links so much I ordered 10 of 'em and used them to secure the EGT and CHT wires firewall forward. Oh, I also powder coated them.
On the lowest screw position on each valve / rocker box cover, I used one of the links. The hole in the link was enlarged to 1/4in. to fit the screw thread diameter. A washer or two, whatever was needed, was used as a standoff to clear the lip of the box cover. The lower hole of the link was used to attach a cushion clamp and the wires that passed by that area.