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Re: 250 i6 fuel economy w/o sacrificing HP
You will typically get your best MPG when your vehicle is running around it's peak torque RPM. That way at a steady RPM, your truck/car is working more efficiently. Sometimes a lower rearend gear (higher number) will get your better MPG. If most of your driving is highway, then you would probably do better mileage with a 3.42/3.73 rearend with the 250. If most of your driving is in town, then I would stay with the 3.07
As far as the engine not holding up to a cam, baloney. Now just just doing a cam and not looking at the rest of a 40 year old motor is asking for a problem.
Freeing up your exhaust flow with headers or a good split manifold, possible an intake and carb change will also probably help. Before I would do any engine mods, I would check my over condition of the engine first. How's the compression, carb settings, timing, etc... As mentioned a good HEI will help. BTW your tire size will effect your MPG also. Large low profile means more resistance, thus it takes more to push the vehicle.
Remember you are moving a LARGE brick. Try things you can afford, but keep the truck running. Don't lose the fun of driving it.
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