takeshi

I generally drive mine back.

They all work. Best depends on what you're looking to do, how much you're willing to pay, what effort you're willing to put in, what you're willing to deal with, etc. I didn't bother at all on mine.

Because Dinosaur

It would be illegal to drive the car unregistered, regardless of whether or not you own it. Temp tags are typically only valid in the state they are issued. When I got some for our S2000 in Arizona, the temp tag was clear that it was only valid in AZ. Now, because of the age of the vehicle, I'm 99% sure you will not be able to registered the vehicle in California without having it smog checked in California. So you can't register it here then fly across the country with the license plate.

I would recommend calling the DMV of the state the car is currently in and seeing if you couldn't get a 30 day registration that would be valid outside of the state. It would be a shame for an expired tag to keep you from an awesome road trip. I've driven two cars across the country now and it's a great time.