Here in PA Classic plates eliminate smog checks. Antique plates, car a little older, eliminate both mechanical and smog, there is a one-time permanent registration that costs $85. NO inspections or annual plate renewals - ever. There is probably a 3 or 4,000 mile limit but I have never heard of anyone being checked.
My speedo and odometer are in KPH - an advantage if they ever check for the math challenged high school graduate these days.
Kilometers, wasn't that a planet in the Star Trek universe?