Magnum heads...what spark plug?

I ran NGK ZFR6F in my magnum. I personally prefer NGK plugs because I find them easier to read. Magnum engines used two different heat range plugs over the years. Earlier engines used a hotter plug (Autolite 3924, NGK FR4, Champion RC12YC, etc) but switched to a colder plug in around 97-98 (Autolite 5224, NGK ZFR6F, Champion RC12LC4, etc). For a while I actually just split the difference and ran NGK FR5 plugs, but they're a little harder to find so I just stuck with the ZFR6F since you can pretty much get it anywhere. Ultimately any of the plugs will work though, so pick your poison.