i have 8 autolite non platinum plugs in it now, need one short plug. I googled the hell out of it and cant find anything other than than those two plugs will fit...taperd seat, 14mm, .708 reach. Both are listed as "header plugs" so i can only assume they both would be short? the 526(s) is double platinum, the 526 isnt. No one has them both in stock to check...