Just a couple of things.

The M112 (your V6) and M113 share the same water pump, and generally speaking the only difference across various displacements and vehicles is the oil cooler outlet. But that's really easy to see, just look at the pump. On the right side of it, the end of it closest to the tensioner, you'll see either an outlet with a hose on it (smaller diameter, I think 3/4") or just a nub where the hose nipple would be. As vince notes it's unlikely you have the cooler, but it's about two minutes to check.

You can buy the pump through the MB dealer system if you like to spend money, but Graf and Saleri are OES and are sold by this site (through Pelican Parts) and are an excellent price. The Graf I bought was identical to the one I removed from my 2001 M112 engine, I think it cost $77.

If you are changing the pump and haven't already, I'd also recommend replacing the idler pulley, tensioner assembly and serpentine belt. All are wear items and can fail leaving you stranded; the original design of the tensioner on your car can also fail catastropically and cause collateral damage.

Good luck.