No need to make a big project out of this. Get a small length of the correct size heater hose. Slide it over the nipple coming out of the water pump. Put a small piece of aluminum bar stock of the correct diameter in the top of the heater hose piece and fasten each end with clamps. This way you'll never have to worry about it leaking again, and it will take all of 5 minutes to fix.

And if sometime in the future, you ever decide you want to hook up the hose to the heater core, you didn't destroy the threads in the pump.