I had a 1976 1/2 ton 2WD LB AT truck with a factory 350 in it. When I wrecked it, I bought a 1980 1/2 ton 4WD SB MT truck with a used-up inline 6. When the inline 6 finally gave up the ghost, I pulled the 350 from the 76 and dropped it into the 4x4. I have rebuilt the carburetor myself with a kit from AutoZone(2 barrel), replaced the plugs and wires, checked the timing, etc (you know, a basic tune-up). I left the 4 spd manual tranny in the 4WD. Also, I know the 76 LB had a bigger gas tank (I think 18 or 20 gallon) than the 80 (16 gallon). But it seems like the 4x4 really drinks the gas much harder than the 2WD--I hit the station to refuel a lot. Is this common--I haven't made the time to pull the rear differential to look at the gear ratio, but this thing is really hitting the old wallet now? Last check on the highway trip to the lake I got just under 13mpg. In the city (with all the traffic and lights) it drops to around 11-12mpg. Any ideas out there?