My bike currently has some cheapo levers installed from the previous owner. I ordered a set of CRG levers, but I have read that CRG (and Pazzo even) levers require the bushings from the stock levers to be swapped over. My question is, what exactly would need swapped over from the OEM levers, and can those parts be purchased separate from buying the entire lever? I do not have the OEM levers, as the bike already had cheap aftermarket ones installed.

 

Yes, you can buy the individual parts and don't need to buy a whole OEM clutch lever. Here is a link to the parts diagram: F4i parts diagram for controls and levers

If the cheap levers on your bike didn't use the factory lever pivot bolt (number 14 in the diagram and the appropriate sized nut) then I assume you need at least that for the CRG's if they don't come with their own hardware.