First and foremost...don't ever put a tag on a vehicle that belongs to another vehicle. This is seen as intent to conceal the identity of a vehicle. Police can impound the vehicle if your story isn't believable.
Can't you just get plates in your state and go down to Florida, slap the out of state plates on and drive it home?If you buy car in Florida, and you DRIVE car home, you must pay Florida state tax, even if you get a paper tag. Then your home state will have to fight Florida to get the tax money back. (I’ve heard horror stories how people ended up paying tax to both states). Only way to not pay Florida tax is to put car on trailer and tow it home.
While that is the simplest way and would be allowed in some states, in much of the east, you risk getting ticketed and the car impounded if pulled over. Ideally you would take the title to your home state to get it registered and get tags and THEN drive it home, but it would probably take 2 trips unless you're buying it online.Can I throw on a plate which is currently registered and insured to me.