I believe Bob is correct. It's probably not street legal in any car. Although, with mods the referees might be persuaded to pass it. I don't really know.
As the other guys posted, you have a better chance of not getting caught if it's installed in a pre-'74 vehicle. It's not that it's legal in pre '74s, it's that anything manufactured before then is not required to go through emissions testing.
If you were pulled over in an RB powered '71 240Z and the officer was able to see under the hood and was astute enough to recognize what was in there, you could still be in trouble.
I had a 280Z that I sold in favor of a 240Z for just that reason. I may still get in trouble but, the chances are less with a 240...