Don't know if any of this info matters but here goes... '70 Nova 350 block. It has an old style LT1 block, out of what car I don't know. Anyway, I just replaced the pump, which I think was short style w/ a chrome one. Both are roughly 7" from the pulley mounting flange to where it mounts to the block. This is a short pump, right?
I just want to make sure because I now have a problem...my water pump pulley won't reinstall because it hits the pump itsself before the pulley sits flush on the round mounting flange. The pulley is 2 groove(Ionly use one though) so I thought maybe the pump is designed to only work w/ a 1 groove pulley and was gonna order a billet one. If I order one, shouldn't the groove that's used be the farthest from the block? That's the one I'm using now so I hope that's the way the new pulley will be. It's 4:20 in the morning so I hope this all made sense.

 

Now I just read that if my alternator is on the passengers' side that I have a long water pump. I'm fairly certain that this chrome one I just installed was supposed to be a short one and measure just like my old one, like I said. But it is passengers side mount alternator too. So I guess it's a long pump, right?

 

A long water pump will have several mounting holes in it to accomodate the passenger alternator, and power steering pump; short pump has no holes; just the ones that bolt it to the block.

 

Even if it is/was a short pump, some of the aftermarker chrome w/p have a little more girth than the stock ones which may cuse fitment problems with the stock pulley. I've run into this problem myself on occasion.

 

I put a short water pump on my old 327 and the pulley would not fit properly at all, I had to sand down the nose of the pump just to get it to work properly, or you could shim it.

 

The dimension of 7" that you gave in your first post is for a LONG water pump. The dimension for a short pump is 5 5/8". You cannot interchange pulleys between the two.