my 86 toyota 2wd got 25city and 30 mpg without trying; full of power tools, fire wood, rocks etc.
the guy who had given it to me, had added some coil springs from an escort front end. he clamped them on top of the leaf springs. i never had any trouble towing a jeep or boat, moving 1500# of stone etc. that truck could take any abuse i could throw at it.
i had the 22r motor, which I loved, but a diesel should easily get 25 percent better mileage, and a veg oil conversion is pretty simple on old toyota diesels. i think with an aero cap and some other basics. your goal should not be a problem
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