Seriously!?!? Please tell me your joking.
Cali already has the worst air quality, the strictest emission laws, and is the toughest place in the country to do a "legal" engine swap. That has got to be the dumbest reason to do a 4bt swap. Might as well throw a little more fuel on the hippie tree huggers fire and work on getting CARB to stop you from being allowed to do ANY modifications to a vehicle.
I personally dont think 1 vehicle is going to destroy the environment, I own a Cobra with an off-road H-pipe, a plow truck with a hollowed out cat (that has been driven all of about 1 mile in the past 6 years), and a few other non-emissions vehicles. I do think that doing something to your truck, just to piss some people off, has got to be the biggest douchebag move you can make.
Its people like you that give diesel fueled vehicles a bad name. If the hippies and yuppies bother you so much, leave California.
FYI: Black smoke = High EGTs = melted pistons ....