oops, almost forgot the most important point - get two caps, get them both painted and put one away. If you don't, I can guarantee that you will leave the painted cap at a gas station or on top of your car within 2 weeks for getting the car painted, and you will run around with a lame chrome aftermarket replacement cap forever. If you have two painted caps, you will never lose the first one!
This is the same theory under which I pack a raincoat when hiking because if I don't the clouds will roll in and drench me before I can get back to the car.