I am installing a new dishwasher in a new space. Its adjacent to my sink. The house was wired for a gar disposal so I'm set for a dedicated circuit. I decided to hardwire using the existing box, and mc cable. I have the cable attached to the box using a 90 degree squeeze connector clamp, and special cover plate made to accept this connector. The cable runs through to connect to the dishwasher electrical box. Am I missing something? Is the average plastic wiring box OK to use with this? I read from one person that a metal box might be preferred.

It usually isn't a problem hard wiring the dishwasher unless it already had a wired plug. When you alter the original mfg. configuration, you void the warranty and also compromiose the UL listing... just so you know.