A link I thank Dan for showing me.. Thanks Dan!

No kidding, there were specific plates for Michigan furniture mover, parking lot, junk truck wagon, landscape and tree operator, garbage collector, and peddlers... whatever that means

I had no idea Michigan had so many varieties in any one year, but the coolest plate they ever made, with red, white, and blue... stars and stripes too, had over a dozen different variants!

License Plates of the U.S. and Canada used during 1976
Click on state, province or territory below to view plates.

http://www.plateshack.com/76/index.html

A bit about California registration too:

1976 was the year that California started staggered registrations. 1975 stickers had been issued for the calendar year 1975, with no month stickers to go with them. In 1976, drivers received month stickers based on the center two characters of their plate.