Replacing the old, overworked exhaust and inlet valves when rebuilding the engine is a sensible precaution, they become brittle and can break off around the valve head area, allowing what is left to drop onto the top of the piston causing untold and very expensive damage!
Refurbishing the cam-shaft drive train at the same time, chains, guides and tensioners, can only improve the final results of a cylinder-head related components overhaul.
Also check the valve guides for wear - one of the most common reasons for a smoking exhaust on start up.
Other parts listed below you may wish to renew at the same time:
120040708
120050710
160070034
490780706
120460564
120460563
120480080
120530161
491180720
920570202
120530162
120530163
491180721
110040084
110080838
110081447
490020009
920551536
920660016
921501368
921530406
921540205
921710729
922001691
921530656
Add as many components as you wish to the same shopping cart, new retainers 120091091 location dowels 92042007 920431264 & new bolts 921501368 (important to ensure correct torque is applied, not easy on old stretched bolts) for example, and still only pay the same single fixed price shipping cost. This component may have other applications within the Kawasaki model range, so check by part number rather than the description. Pro-workshop gasket sealant 08C70K0234M easy to apply with pleasing results.