Best way to remove nipples on water pump?

I sell water pump housings with the nipples and plugs removed, so I've done a few in my time!

First, I remove the water pump housing BEFORE applying the acetylene torch. Work it on the floor or the bench and keep excess heat out of the engine.

The way to remove the housing without unblocking the bolt that the nipple obstructs is to take out all the OTHER bolts first! Then use an open end 9/16 wrench to start to remove the blocked bolt. You will find that the head of that bolt will push against the nipple that's blocking it and break loose the gasket seal. Eventually the housing comes right off (with the bolt still behind the nipple).

After the housing and water pump are out, you can apply all the heat you want to the nipples and they will eventually easily turn out. I do occasionally crush one with a pipe wrench, but it is the housing than I'm after. The nipples are available new.