Mesa Mike- Are you sure it's the water pump that's leaking? Is the coolant coming from the weep hole, or is it coming from the gasket flanges?
Are you cleaning the bolt threads with a die or wire brush, and re-coating them with silicone before re-installing them? The 4 bolts that hold the water pump to the block all extend into the water jackets - They need to be sealed or they will leak back through the threads...
Also, if you haven't already, you might want to replace the T-Stat housing gasket as well, and if you have an aluminum water neck, then take a real good look at it for fine cracks - If the water neck is leaking, then the leak will usually run down along the water pump flanges, and can look like a water pump leak from the bottom...
Just a few suggestions for things to look for (if you haven't already...
- no offense intended if you've already covered all these bases) - I'm not a big fan of "leak repair in a can" so that should be a last ditch option if the true source of the leak can't be identified and corrected.
I hate chasing leaks as much as I hate chasing electrical gremlins... (well, maybe not THAT much, LOL )