Few questions,
It needs a top end I think (pulled exhaust and had black below the rings like maybe from blow by)
So are the Pro X pistons any good?
I wouldn't.... get a Wossner...
Do you need to drill any holes in the piston like on the CR500?
No, but there are some really cool mods you can do with holes.
Are the cylinders bore able like the CR500 or are they plated like 250s?
They are plated unless yours has been sleeved aftermarket.
You won't know till you get it off.
I remember seeing the pistons on here that some one cut a window in, why? Do they have any left?
The school is out on that. Going back to holes in the piston there are some really cool things you can do with holes in the right place.
PM ALWARD25, he can give you details on a piston.