This is not true. Mallett's conversions are the closest, out of the shop, to being registerable in California, but you'll need to take it through the referee. Mallett's conversions were NOT a GM option. Their broad use of the GM parts catalog is a big help, though!The beauty of the Mallett is the ability to register it here in Cali due to the fact it is a GM titled option with EPA stamp! Will be here once reliable carriers has a pick up date confirmed.
You'll need to take it to the Smog Referee. The one in Livermore wasn't so bad, but you'll want a full set of 2007 Corvette service manuals. Mark the pages with illustrations of the LS2-style exhaust manifolds and catalytic converters, because you'll need to prove they're the right ones for the car. Always be very clear that the drivetrain is 2007 Corvette. I think you could also claim 2007 CTS-V if the manifolds match (I don't recall if they got different ones than a Corvette LS2.) If it's not a 6-speed, hope the referee doesn't notice (as this can be something the referee can choose to fail you over.) Technically, even not using the same transaxle as a Corvette could be a fail reason.
Get a scan tool that can show the status of the ECM's readiness tests. You'll need 4/4 set to get through the referee, but your subsequent biannual tests can do 3/4 and pass. EVAP takes FOREVER to mark as complete, and you need to do some pretty specific driving to flip it on. Sucks to drive all the way there and find out you weren't gonna pass the electronic portion of the test. The ref will also want documentation that you're using the proper ECM & calibration. Mallett revised the ECM used over the life of production, you may be using a GMPP crate motor ECM that doesn't properly implement OBD2 protocols. They may complain about the VIN, since Mallett will have stored a Solstice VIN in the ECM, and they'll be expecting a Corvette one. This is resolvable, I had to call and talk to a supervisor, and then I passed the next time. (They may be more open to this now that I've paved the way.) Explain that it's a new motor, not a salvaged motor, so there's no donor VIN to use.
You'll be on the dyno. The engine will be VERY cold, as the earlier visual inspections will be a couple hours worth of time. If you get your exhaust system ceramic coated, the cats will light off faster, and you'll be more comfortable as the center tunnel and floors won't get as hot. It's good insurance that the dyno portion will be your friend!
Verify yourself that all the routing for the PCV, EVAP, etc are in place. Mallett did this right, but you're gonna have to be your own advocate at the ref!
It may take a couple passes, but the state only charges $8 for the whole thing no matter how long it takes! The requirements may seem tough, but they're actually pretty reasonable all-round.
Don't drive it on old tires!
Energy Suspension's differential nose bushing helps the rear end, but I think they are NLA. If you can find a Z0K crossmember, that's preferable to the alternatives, but they're pretty thin these days. I also had a local shop build me a differential cooler, but my Mallett sees a lot heavier duty than cruising and car shows.