At the risk of sounding like a chant.....Buy the JTR Book....Buy the JTR Book.
I had an early edition and it even had a chapter on smog laws (especially California). AS long as the transplant engine the same year to or newer than the car body, with all factory smog equipment intact, you're set and it'll pass. California 280's had catalytic converters, and so will your donor vehicle, so you'll have a cat or 2 in the exhaust system anyway same with Air pumps, charcoal cannisters, EGR valves - whatever. I feel the best source is a TPI 350 pulled from a Camaro / Firebird. (Say "Corvette" and pay 2 prices). But the thing about hybridZ is YOU build it to suit YOUR taste and budget.
Ever hear Bill Cosby do that routine about the car he built with Wierd Harold? ....used a Cessna airplane engine out of the junkyard...... he does the sound effects so funny and the story captures the spirit of a hybridZ, determination, resourcefulness, pride of ownership.