Ok........I've been down this road when I lived in California.
The first two questions to get answered are:
1. Is the car a California emissions car or a 49 State car? Have them send you a pic of the emissions sticker under the hood. If it's a "Federal" or a
"49 State" car, the Calif smog stations have the smog calibration for that in their computers and will run that program vs the California program.
2. Is the transplanted engine the same year as the car body? Newer? Older?
a. This mattered when I did my transplant because if I was just "replacing" my old engine with either a rebuild of my old engine or a same year
engine, then I didn't need to do anything special to smog and re-register my car, and no one was the wiser.
b. If I was using an older engine in the car, then I would have to make that engine match the smog requirements of the car body (you can't go
backwards in smog compliance).
c. If I was using a newer year engine (which I was doing), and wanted to use the newer smog equipment (newer style cats, etc), they (CARB) had
no problem at all since in their eyes I was updating the car to more modern smog compliance. I was using a newer crate motor in my older car
because it had more power, I could legally equip the car with true dual exhaust, I was using the newer computer system, etc. This was important
because the new crate motor had the "Calibration Sticker" for that engine and the computer would show that as well. This is probably related to
what was mentioned above about "tune check".
This was my experience years ago. I talked to someone at the Air Resources Board before I purchased anything to make sure they weren't going to give me any problems with what I wanted to do. I think I threw them for a loop when I was actually wanting to put a newer engine and newer smog equipment into my older car when most people were trying to do the opposite.