I have an air gap on my 360, the magnum head version. It has a Summit K6901 cam witch is 218/228 duration at .050" lift and about .470" lift at the valve. I have a 4-speed and this thing idles "stock" smooth at 800 rpm. I'd also be lucky to have an 8.8:1 compression ratio.

The air gap works great. make sure your choke works properly. My car has a 600 holley electric choke.