Is my 340 Overcarbed? Avg 5-6 MPG

OK here is the update for tonight. I pulled the primary bowl and jetted down to 70's since that was all that my builder had. I also dropped the float levels on the pri and sec bowls since they where half way up the sight glass. I lowered them both to the bottom of the sight glasses. I fired it up and adjusted everything for idle. I went for a test drive and holy **** there is a in the seat difference in power. Putting around the wideband was seeing 13.2. I took her out on the freeway and went to town. I nailed it WOT and AF was at 13.7 the entire range. I backed it off to cruising speed and at 65 mph/2600rpm the wideband was fluctuating between 13.2 and 13.5. Everything is now in the green throughout the entire range. I reset timing back to 14 as it was not liking to be advanced. My only new issue now is my 1st gear has a huge hesitation and stumble. It did not have this before. Is that a accel pump adjustment? Why would that all of a sudden come out? As far as the plugs go, my builder said that all the soot is from the engine idling too long from when he tuned it on the dyno. He said it saw a lot of idle time and with that cam it makes sense. I put new plugs in it just to make sure so I will keep an eye on that. So this has been a good evening so far. Just need to fix that low speed hesitation/stumble and I will run a tank through it to see how it does. Thank you all very much!