I imagine that there will come a time when they’ll need to revert to horse and wagon transport at the site. Or perhaps lay down railroad tracks and use cable cars.
Engines produced for industrial applications (such as tractors) in developing countries still use this, as it's a lot simpler and more reliable. Military trucks are the same. Just don't tell the EPA.
Main problem, in those countries have not managed to produce small diesel engines for light trucks, and KRAZ engines are something 6L or more (tank diesel are 10L).
I hear they made half-block near-flat modification for armored personnel carrier, and even used it on low-floor city bus, but as I know they was not much market success, so have not produced big series.
I might have to wind a generator motor if the reason stuff went bad is because of emp, but otherwise, yeah, you can buy 100% mechanical diesel engines still.
Not a great idea, those engines like to blow holes in their pistons...