[Bruce Edwards]

It is a bit on the high side but if the carb does not overflow you should be ok. Check your timing and plug wires for cross fire. Open the hood and start it up at night in a very dark area. Look around the plug wires for a stray spark.
What kind of plugs are you running?
A sigh you may be on the right track is that the plugs should look cleaner and you may see a small rise in the water temp due to better combustion at lower speeds as well as better take off.
Any pinging under load?
Is the vacuum nice and steady? 12.5 is pretty good and 6.5 would be pretty close. May want to go to 6 to be on the safe side.
Let me know what you find out.