Legally Register Any Car

So, possibly, "technically" you Could roll "somewhere" get a bill of sale, and registration, THEN a tag from That Place, and just drive it in Your Home State?
You need a valuation as well. Thanks to Kelly Blue Book changing their valuation tool, any car I'd want is way overvalued, and I'd pay more than I want on tax of the claimed value. (They use auctions to come up with a price, and those numbers may not accurately reflect a project car's value) They won't just take your word for what you paid, you need a baseline. That's my main hangup. But other than that, I think, that's all you need.