you can get coolant test strips at NAPA to verify that additives are still healthy
cummins was not too prone to cavitation, but it is worth checking, and certainly worth maintaining. There are quite a few fixes to get free power from this vintage, and truck is pretty stout, tho tend to rust. (Cab pillars / floors) Check for a broken steering box mount, Mine's welded...
wiring is not great, but a $5 relay added in headlight circuit solves the biggest issue.
good dodge info here; www dieseltruckresource com ; look in 1st generation forum
These are mostly 'mechanical', diesels so pretty simple to fix and maintain.