If you have the serpentine belt, you need the later (92) water pump. The serpentine belt turns the water pump backwards compared to the old (90) "V" belt drive.
You can tell by looking at how the fan is attached to the water pump. If it has one big nut, it is the serpentine belt and the later pump. If the fan is attached by 4 bolts, it is the "V" belt drive and uses the older pump. Your truck uses one system or the other, there was no "mix", it was a complete change over when the serpentine belt was introduced. Gene
Wrong, I have a 91 dakota with a V8, it is a 1 year 1 aplication deal, it has a serp belt but the fan is not atactched (well it actually is now as I had the same problem getting the right water pimp) with the one big nut like 92+ magnum, also the way all the other accessories are bolted on is one year one aplication as the 91 ram and full size van still used V belts. The oil pan is also 1 year 1 aplication.
