you're not going to get hassled without going for a non carb exempt header in cali. though it's NICE to have the carb exemption, I've never had an issue, nor my bro, nor my friends. Cali gets a horrible rep, and is not nearly as strict as anyone makes it to be. "most" techs here don't give a damn about the visual. my buddy rolled right in with an 85gt and a 86+ dual exhaust conversion, which is "technically" not legal. not a single problem, they passed him right on through.
as for the H pipe, magnaflow makes the ONLY carb exempt and legal mid pipe, it's their 2 catted x pipe, and comes with a carb exemption #, so you're completely fine to swap out to that. I'm currently saving my money for that, and my bro already has one on his car, sounds quite wicked too!