EMP doesn’t permanently damage vehicle electronics - both Mythbusters and Top Gear showed cars being hit by direct lightning strikes which is orders of magnitude greater current loads. The cars stopped, but restarted easily.

Modern diesels are worse than modern gas for electronic controls bullshit - they stop working over the littlest thing - this is how they achieve their fuel economy and emissions. (So would still be affected by EMP too).

That said, an older diesel using a mechanical timing pump is what you want. They run forever and can tolerate poor fuels.