Sounds right. I'm pretty sure the Ram350 I drove was an '87 and it had an ammeter. dumper and plow were both wired to the battery. At the time didn't understand why so much current would flow through it when the raising the bed.
'85 was the last year for AMC's Grand Wagoneers to have ammeters.
'86 was the first year of a redesined wiring system. Power distribution began at the starter solenoid. Lots of fusible links.