Is my 340 Overcarbed? Avg 5-6 MPG

Of course this is not what I want to hear right now, but I value everyone's opinion here so that is why I am leaning on you all. The reason I took this engine to a professional builder was to have it done right so I am going to take a trip to go and see him tomorrow. He recommended this for my setup so I thought I was in good shape. If I have to re-cam or re-carb this thing, I am gonna be pretty pissed off, but I will do what is right to make it right and put out the horsepower. I thought the dyno HP was on the low side as well, but I am not smart in that department. I wanted a built, healthy small block. Frustrated...but still receptive...