There's almost too many at the pointy end to choose from.
Apart from the unobtainium (RH), I'd go w the lightweight weapons - ie any one of the spanish: 
'Sang, Phantom or VR perhaps in any order. They had the handles, suspension, power & (lack of) weight.
A hairs breadth behind would be KX (w suitable suspension mods), F11M & YZ-B
A nose further back would be a CZ (tricked out), MAG & KTM
Then a TM-L,  'Snore, DT2M, 73MX, Maico, Cooper & Canam - each w suitable mods
But you could throw a blanket over the whole lot - well, most of them. 
Just splitting hairs really.  
I'd be happy with them all...  I mean, any of them.  
Heck, I'd even have a quirky Brit - Rickman or Ajay Stormer. (Probably not a Greeves or Sprite tho!)
And weren't there a couple of Italian stallions who just snuck in before 75?