Try adjusting your valves. I was working on my wifes truck awhile back and had 1 or 2 intake valves maladjusted and the fuel economy suffered horribly. This was on a 307 with a Q-Jet from a 350. Once I readjusted them properly the mpg soared from about 6 mpg to about 14 in town. One of those things you learn by trial and error. Oh well...
Jeff
