No problem with the questions. I think you'll find if you ask right and respect the opinions of those who respond you'll do just fine here.

As to the Air Gap - not sure what you're looking for. Your 305 will probably not see a lot of benefit from this manifold as you're probably out of motor about 5000RPM.

Get your current combination dialed in and drive it for a while. If you're not satisfied, a Performer RPM and a Q-jet would probably be a good fit.