ok, i have a 302 ford but a belt is a belt and a pully is a pully
i'm running a Vbelt with the ribbed side on the flat water pump pully, i dont think it will fail or throw the belt, but it will slip alot giving that squeeky annoying noise whenever you start the car or rev it.
here you can see how the belt marked the WP pully
installed
i would recommend that you buy a water pump pully with grooves, that's what i did, i ordered mine from summit and its about 79 bucks. http://store.summitracing.com/partdetail.asp?autofilter=1&part=MCH%2D2004&N=700+0&autoview=sku
check them out.