I am pretty sure the CA cops are more concerned with the more modern cars with younger drivers and obnoxious exhausts, way too low stance, flashy paint, flashy wheels and flashy body kits. Easy targets, that stick out and cops "do profile" (unfortunately).
The Z being such an old car and really classic car, will draw very little if any attention unless you are bringing attention to yourself with say aggressive driving -or- in a convoy of flashy cars, where they will pull everyone over and check over each car carefully.
If you are worried about an intercooler what about exhaust, I am sure having a L28ET on your car it has a louder and larger diameter exhaust?
If your car is a '75 or earlier, you have even less to worry about.
As mentioned by Vintage you can spray paint or powder coat it black to make it less conspicuous.
With the heat of California, I would NEVER run a turbo car without an intercooler.
Bo..car is looking great as usual!
Yasin