im replacing the pcv hoses, valve cover gaskets and timing cover gaskets - what else should i replace whilst being busy towards the back end of the engine?

should i replace the following:

- radiator hoses, including O-rings both manifold to large tube and small tube, rear water return hose to heater
- camshaft variable timing solenoid
- intake manifold rear end plate
- what else?


is it necessary to replace the rear end cover of the intake manifold or only the gasket.