Title pretty much says it all- I've got an '85 2WD C20 with a 14 bolt rear end and 4.10 ratio and I do highway driving almost exclusively. I'm getting 10-15 mpg at most with my 350 motor, AT. I'd like to do better as it's 250 miles RT each trip= expensive! I can get a 3.71 pumpkin from a newer (newer than '91) 14 bolt rear end, a 2500 2WD. Can I simply pull the axles, cover, input and swap out for mine? That way I think I can keep my housing, axles, brakes, etc and not move 500 pounds of iron back and forth from the wreckers. Anyone have experience with this enough to advise on fuel economy for highway driving? Wheels and tires are as original equipment, commercial tires on 16" rims. Tire pressure is as recommended (80 PSI rear) I did a similar thing on my other pickup, but I knew those to be interchangeable in advance and owned the parts already, anyway.