If you make it EVO the Husky 510 1983/84 is still way better than any special built bike. It would have to be pre 78 to protect all those 70's specials. I am all for pre 85 but that is my opinion. People build bikes to suit the rules. Make it EVO and you will see Maico framed specials Huskies etc. They will still flog a lot of the early specials. Make it pre78 Then heaps of latter bikes miss out. Make it pre85 everyone can ride. There will always be bikes that do not fit the class or are not competitive, but that is the case with all VMX racing.