Air in cooling system

On my Manta Mirage I have a carb 350 and I'm trying to understand the mechanics of the cooling system and work through a resolution. What I mean is that I always thought you could not have air in the system, but I have no coolant reservoir and there is no way for me to fill the system without air in it that I've found.

#1 - am I correct you should not have any air in the cooing system

#2 - does a coolant reservoir need to be at the highest point in the system

#3 - anyone have a possible resolution/suggestion

So I've been looking at some universal cooling expansion tanks. It appears I'd have to have the tank at the highest point. In the attached image you'll see the way I have to fill the system. It is not the highest point and I believe I am getting vapor lock. I'm thinking of mounting a universal expansion tank in approximately the same position so when the engine hatch comes down it will tuck up into the wings of it and stay at the highest point.

I'm running a coolant filler cap designed for sprint track cars, which contains the thermostat housing, coolant hose connection, filler cap, and expansion tank connection in one piece. It mounts directly on my Chev small block intake manifold, which coincidently is the highest point of my cooling system. No real problems noted. I also have installed a petcock on the top of the radiator, to bleed off any air that may get trapped there (the second "highest point" of my coolant system).

Ken do you have a picture of this or a link to the product by chance?