273 Commando Spark Plug Wire Options?

I have reproduction insulators on my 273, but I believe originals to be the same. They don't push in, instead you rotate the insulator so that the flat side is 90 degrees out from the top of the valve cover and it drops into place. Turn it back so the flat of the insulator is at the top (parallel to the top of the valve cover) and it locks into place. If the insulator is too loose on the wire, you can increase the diameter by installing a short length of shrink wrap on the wire and the insulator will be tight once snapped onto the wire.