Spark Plug Advice Needed

I put a timing light on it yesterday and at idle the engine is really happy at 35 degrees advanced and it has 20 inches of vacuum. I tried to check the advance at idle with the 16 initial and connected to manifold vacuum but the bulb burned out on my timing light.
I was told by FBO when they set my distributer to switch to manifold vacuum. It gives me more control over the mixture screws, and reduces transfer slot exposure to vacuum. I can kill the engine with the mixture screw.
I'm going to buy a couple spark plugs one heat range hotter and run the car on the expressway with a clean cut off and I'll cut those apart. That's going to have a lot of new information.