I am not positive but I think the one you are looking at buying is so powerful that it causes the fluid to foam unless you put some restriction in the system.
Do a quick search. There was a thread where it was shown to work well. It isn't too powerful and doesn't flow too much nor foam up the system from what I've read on the GT500.
That being said, I have the C&R radiator, heat exchanger, and larger heat exchanger coolant tank but stock pump. Zero coolant issues and I'm in Florida. The radiator is a great upgrade.
I was at work last night and posted my link quickly hoping the OP would look at the whole thread and see the comparisons between the pumps. I didn't realize it was on the page talking about the foaming/restrictors. It looks like the foaming was caused by low fluid level. It looks like people are also putting a higher ration of water in the system to help as well.