Need help tuning a 273.

Yesterday I warmed up the motor. Plugged all vacum ports on the carb and set the timing to aprox 12 BTDC. The motor idles at about 500rpm. Is that a little low maybe?

I then attached the vacum hose from the distibuter to the higher of the two ports on the carb like you suggested "Fishthatkills". I could only feel vacum in that port when I reved the engine.

It runs much better now, there is still some hesitation if you stomp it from start though.
I dont know the total timing either, the scale runs out, so How do I set it?
A friend checked with the timing gun when I reved the enginge and it stopped climbing around 3000 rpm but it is just a guessing game where it was.