"street legal" varies widely from state to state, and sometimes even county to county or in various cities due to local ordinances. You'd have to look up your local ordinance or state law and see if your mufflers exceed the decibel limit.
I run glasspacks on my Challenger, they're a heck of a lot louder than 40's. And they sound about a million times better too.
No fix-it tickets yet, knock on wood.
