If you live in PA you have 3 choices for your car.
Run regular plates, annual inspection, emissions and registration required
If it is 15yrs or older, you can have classic plates, inspection & emissions required, but no registration(permanent registration), some limits on how often you can drive it
If it is 25 yrs or older, you can have antique plates, no inspection or registration required(permenant registration). More restrictions on where you can drive it.
Since I don't even put 1000 miles on it a year and I have recently replaced everything on it they check for inspection, I went with the antique plates. I know it is safe, I don't need to pay the state to tell me the same