I picked up this beast of a pickup over the winter.
1980 Chevy K20, aka The Mule. 3/4 ton 4WD with a gas 5.7L V8 and 4-speed manual. It's really a 3-speed with a "crawler" gear. Originally from Arizona, but starting to rust after a few years in NY.
Not driving it saves the most fuel. It gets single digit MPG towing at 45-50 MPH! The first planned mod is more displacement. A 6.2L diesel V8.
That alone should get me an additional 5+ MPG.
Axle ratios are 3.73. And there's no overdrive. I wanted taller gears until I towed 4000 lbs uphill. I don't think the weaker diesel could handle taller gears. An overdrive transmission would be nice, but they're hard to find at a decent price. So gearing will likely stay as it is. I'll just drive slow.
It will be converted to run on WVO and I'm thinking about an aerocap. Any other ideas? Is synthetic gear oil in the tranny, transfer case and rear end worth it? I'll be plowing snow with it, so I can't lower it or do much with the horrible underbody aerodynamics. Maybe an airdam? Since I'm planning to use the much smaller gas radiator, a grill block is probably a bad idea.