Rick55,On the subject of Mac's B6A-6549-C rocker arm adjusting screws, their photo shows that part likely has a zinc finish. OEM's did not. How is the quality and wear?
Reason I ask is Mac's have the same shinny finish as ones I bought from Tee Bird Products sourced from Elgin back in 2008. Those had oversized soft ball heads that wouldn't fit fully in the push rod cups without grinding, an oversized thread diameter that required a 1/2" socket handle to install them and break them loose again to gap a valve and an under sized soft nut that requires a six point socket to avoid rounding off the corners. These things loose gap in less than 50 miles. Once you screw one in and out, you can forget ever using an OEM friction screw in the rocker again. You can screw on in all the way to the hex head with your fingers. I relayed all this info back at the time. I just recently spoke with them. They still can't find any other source. I bought 6 at the time. All 4 I didn't use and the 2 I did are going in the trash as soon as I locate 3 OEM lock nuts, p/n EAA-6552-A, to lock the OEM friction screws their loose fitting rockers. They can't get lock nuts either.
Jerome