The OD of the spring locator on the cast iron head is 0.994". The ID of the valve spring is 1.06". Not much room for the locator shim. If the head were machined for viton seals this would be easier.
When I switched my buddy’s heads over to LS spring package I had to cut them down for .500 seals. them I had to use negative retainers and keepers to get enough spring pressure for a .660 lift cam. .060 coil bind do we cut it close. PAC was satisfied with how they were set up.