You have to run all the correct smog equipment, which isn't much on an M5X. Basically just the charcoal canister. Converting a OBDII engine to OBDI is technically illegal. You must tell the referee the engine is either a 2.5 or 3.0 when smog time comes.
Basically, the process is simple. Install the engine, make sure you have a good cat, and charcoal canister hooked up. Call up the Referee (800) 622-7733 and make an appointment at your local station.
Take the car, make sure the cat is good and hot, and they will smog it just like a normal smog. They will ask you what engine you used. Do not say 3.2/2.8 OBD1 conversion. If the car passes, you get the sticker that says you are legit. If you do not pass, you just repair what is needed (my car just failed with very high HC and NOX) and go back. They are always helpful as they like seeing newer, cleaner engines in older cars. Remember, this is a state funded program, they want cars to pass. If you have any other questions ask, if i remember anything else I can post.
Once you get the Referee sticker, you are free to get smogged at ANY smog place the next times around.