The K factory clutch does not move the engine back, it will not affect the fuel tank. It does extend the clutchbell forward slightly, about 3-4mm. If you are running an aluminum lower suspension mount, it will interfere with the clutch bell. Hope that helps.
Rookie Solara, I did not buy a whole clutch assembly from powerlineracing.com just a couple of pinion gears. I bought 2 brand new K Factory clutches off of EBay for less than $60 ea.