I have always reused intake bolts when installing intake manifolds. Some aftermarket intakes may need different bolts then the original intake, but in most cases they are included with the intake. Intake manifold bolts aren't torque-to-yield bolts like 5.0 head bolts are. Just make sure they are nice and clean and the heads are good and not rounded off (to prevent any future problems) and you should be good to go.