P heads were on the v8 explorer/mountanier and were actually supposed to be cleaner then the reg gt40, were on the 96-02 in fact when most cars had switched to a 4.6 due to emissions. the gt40p should be no problem to get to pass smog in any of the 50 states since they were on 50 state legal autos. I would however not get them if they have been ported as that can change the smog outcome.