340 Gets Terrible Gas Mileage

My experience with LA engines has been mostly great. I drove a mostly stock 340/4spd/3.23 combo back and forth to work for about 8 years. City mileage was 10-12. Now my '85 D350/360/727/4.1/dually usually gets 7-8 mpg in town and If you drive 55 on the highway you might see 10mpg. So yeah the OP needs to find someone locally to sort his combo out. I hope he finds somebody!