I bought mine in england for the exact price too...

Bushing bearings on camshaft is not only on thunder tiger.... I've heard Saito uses bushings there...remember the cam rotates half the speed of the engine.

The Bushings I think are not easy to remove if they can be remover at all...you'll have to mill the crankcase and the cover to accomodate the bearings....but I would bother neither.

I've tried the 12x7 and yes, the engine does rev more....but I don't see the point running the engine with a prop that a 75 2 stroke usually spins.... I would load the engine more.