it's a bike in england and it is a very english thing to paint everything green (maybe that is why it is its racing color). The tail section is off the old generation triumph speed triple and I am not too fond of it either (it's bigger than the tank for chrissakes).
The problem with a unlimited vintage class is where do you draw the line? Just suspension? aftermarket frames if they are period (rickman, dunstall, etc)? frame bracing? engine mods (Kz engines can be bored and troked to 1200ccs, cb750s can go 1036cc, lets see a brit parallel twin keep up with that, even with a dunstall 910cc norton kit). what about the 2 smokes (modded h2s are the fastest 2 three cylinder engines in drag racing and modded street bikes make over 100 hp)?