The rules state in clear english "ANY period flatslide". My bike is 1982, the carbs were available in 1982, maybe earlier. The evo "period" ranges right up to 1984 with certain manufacturers. The way I read it, it is a legal period carburetor. I asked a simple question to clarify and opened a can of worms. Lots of differing opinions, but no clear answer forthcoming. It's not about building a bike outside the rules at all, it's a legitimate inquiry. Next someone will say a 1984 Husqvarna CR500 is a pre '85 bike even though it meets all EVO requirements. Maybe the evo rules should be amended to no linkage, no water cooling, drum brakes, built before 1985.
To answer your questions Brent:
Could I fit a flatslide TM to my 1982 EVO bike in 1982, yes. Could I fit 1984 MUGEN or Simons UXD 60's to my 1982 EVO bike in 1982, no.
BUT could I fit 1984 Mugen or Simons UXD60's or WP40U's to my 1984 EVO bike in 1984, YES. So there's an even bigger can of worms.