1996 Seville water pump

I have a 1996 Seville, I'm trying to re-place the water pump  is there a certain way to re-install the pump? Every time I put it back together the fluid pours out the back of the housing. I've replaced the o-ring, cleaned it out. Is there a certain way the clips on the water pump have to be in order to securely fit in the housing? Any help would be greatly appreciated.

Are you using special tool to install pump?

Yes, I'm using the special tool. One of the retaining tabs are different from the rest. Is there a certain spot in the housing for that tab?
 
Thanks for your reply.