Should I have an overflow bottle?

If you have a radiator cap with two seals (one on the spring, the other on the cap itself) by all means install a recovery bottle. Most of the caps I've seen at the big box part stores are for closed systems, so they will work.

If you have only the cap seal, the system sucks in air. You'd probably need to spend $s @ YO or someplace with NOS parts to grab one of these.

Ideally the recovery bottle will have an overflow outlet that will allow you to protect the rest of your engine compartment. The recovery bottle will also need to have a tube that connects the radiator neck to the bottom of the bottle. Otherwise the recovery bottle becomes an overflow reservoir.