The grinding & fitting is mostly required when installing headers and/or aftermarket intake manifolds. It can be time-consuming and require lots of trial & error.
Kansas Kustoms does great work and can repair a bad heat riser in most cases. An unheated intake invites driveablity problems. The water heat vs exhaust heat issue applies to aluminum aftermarket intakes only - at least on 235s (Early Datsun 240Z's had water passsages cast into the intake manifolds). Water heat provides a more gentle, consistent heat source but will require some planning and thought to how the hoses will be fitted and routed through the cooling system.
