Should I have an overflow bottle?

Put a bottle on it, itll suck the water back in when it cools. Prevents nasty rusty water from being spit out onto your driveway and rad support too. Just dont seal the bottle, they sell the plastic fender hangers for about 8 bucks at chain stores and it comes with a cap and hose.

If you go this route, which I personally think isnt bad, make sure you drill the inlet hose. both me and a buddy got ours and they were not drilled, thus rendering the things useless until we did.