I did Body & point work for almost 40 years, I don't know anything about Diesels...
1989 Dodge D250 Cummins Turbo 12 Valve Automatic 2 speed... All stock... The Battery was "bolted down" backwards and burnt out 99% of the wiring - Engine - Dash - Lights... I had 2 batteries " Blow-up ", fireball shot out and sounded like a bomb... After a year of patching wires and replacing relays... I finally " Cut every wire from the engine & dash " the only wires left is the Alt and I don't think that is hooked-up because I took out the PCM...
It's Hot-Wired, FSS to battery - Run Starter solenoid to battery... I hope it don't mess up anything...

 

Welcome to Diesel bombers! great thing about the 12 valve's you could hit the starter with no other wires attached to the engine and it will start . great motor tried and true.