If money isn't a problem, buy yourself a Minarelli engine from sip and get a little Hebo replica on it and have fun
but any cylinder for minarelli will fit as well as exhaust. but for variators and gearing you'll have to ask a Pro, from what i know the crankshaft on variator side is different than the minarelli one.
Cylinder, exhaust, reed valves, manifold - same as minarelli everything else is different.
rule of thumb, get yourself a ex. pipe first, then a variator(MAlossi) then a racing cylinder + Bigger carb