Best plugs for Magnum heads?

I use magnum specific plugs in my magnum headed 360. These are a 5/8" hex plug but the thread and reach are the same as your 65's. The smaller hex allows a socket to fit between the header tube and head easily.

I have a 10.6:1 360 and have tried the stock heat range Autolite 5224, the shorter nose 3924 and the colder heat range short nose 3923 plugs. There does not seem to be any difference in the way the engine runs so I have settled on the 5224 plug.