Water Pump Pulley Mounting Problems

[engrdean]

I have had the water pump off of my truck for a while now and recently went to put things back together this last weekend. Since I originally had it off, I have either lost or mistakenly thrown away the original water pump. I have gone through several different pumps in an attempt to replace it and think that I have finally found the right one. All of the brackets line up great for the AC, however, when I went to put the pulley and fan back on, the bolt holes do not line up. The shaft size is correct, but the bolt holes on the pump where the pulley mounts are spaced about a half inch closer together than those on the fan and the pulley which I took off the truck.

Do I still have the wrong pump? Did the mounting hole spacing change at some point over the years? I don't mind going to the salvage yard and looking for a fan and pulley that will fit, but I am worried that it won't line up with the rest of my pulleys if this pump is for a completely different vehicle. This seems unlikely since everything else lines up perfect, but I guess I am just trying to figure out if I did something wrong or I can keep moving forward as is.

The truck is a 1970 C10 with a 350, all stock. The water pump was bought at a local parts store and I am not sure what the brand is. It is a short style pump which I am fairly certain is correct (the AC is on the passenger side of the truck). I would appreciate any thoughts the experts out there might have.