The 5.9L 12-valve Cummins is also a fine choice. Another fully mechanical engine. In theory, with a manual transmission, you can operate a vehicle without even a battery after it's started.
Well, almost. The 5.9L fails safe: there is a fuel shutoff solenoid which operates in reverse: you give it power to keep the fuel flowing. You’d need to modify it to force the solenoid open (or remove it).
The OM617 (as used in many 1980’s Mercedes sedans) fuel shutoff operated on vacuum, and once started, the engine would run with no electrical system at all.