The current Fox .35 Stunt is legal for SAM Foxacoy and is substantially the same as the original 3-screw backplate versions. The most noticable difference is the provision for muffler mounting, and a "50th Anniversary" logo on the bypass. I've seen several different needle valve assemblies and thrust washers and maybe a different head or two, but don't believe the internals have changed. I haven't heard that any particular version has a performance advantage, either.

I haven't worn one out yet, but they seem to take forever to wear IN