I have a 440 source water pump and housing too. It seems to work fine as far as cooling is concerned? I had to machine 3 parts on it before I could use it though?
Did the impeller seem tight when installed it?
I drill a small hole(1/32) off to the side of the thermostat before I install so I don't have to "burp it" as Jason said?
Do you have a shroud on the fan?
Does it overheat all the time of just in traffic? what temps are you seeing? Stock gauges or aftermarket?