Is my 340 Overcarbed? Avg 5-6 MPG

It's still fat on cruise and I hope you didn't hammer it with the initial timing at 20*+ and no changes to the distributor.

No I didnt, timing was back to original during that run. I will pick up some 68 jets from an auto parts store today and jet down again. That seems to be working the lower I go. The engine is not liking to be advanced at all. Not sure on that one. Plus the more I advanced it the more total timing increased. Seems like jetting is heading in the right direction and power is coming up. Should I be messing with secondary jetting at all while dropping the primaries to richen up WOT or a spring since its vacuum secondary?