Any mid-eighties Mercedes with the 5-banger OM617. They are glacially slow, produce the horsepower of a tricycle, and are loud as a bomb... but they don't die, and I respect that. Everything around the engine will rot away, and you'll likely get tetanus from looking at it wrong, but the engine itself stands to rival the other engines of the post-apocalypse: the Ford 300, Volvo Redblocks, Chrysler Slant6, and the 1UZ-FE. After the apocalypse, you'll still see old W124s chugging alongside the F150s, Volvo 200s, and '67 Valiants rumbling along through the remnants. I mean, I bet this one will even start up if you tossed a battery and some fuel in.
I knew it was a Volvo, but it was the closest thing I could find. They aren't that different, especially with the discernible features bleached out by the flash of the nuke.
I'm sorry, but a vehement NO to the pickup truck. Germans shouldn't make trucks. Leave pickup trucks to the Americans plus Toyota and Nissan.