Like some others said- look up the plug cross reference. I know a lot of folks hate the champions but I've been usin them for years in everything. RC12YC. Fits my shovelhead, my triumph, my eddy headed LA 408, my iron head LA 318... You get the picture. It has a 5/8" hex on it which works great for tight header reaches etc.

I noticed that at least with the champ line there's a one letter difference between 5/8 and 13/16 wrench plugs and no other difference. Like RC12YC is what I use but RN12YC is the fatter hex'd plug.

Worth a shot.

Good luck
Radar