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I put mine in on the 5/8 return hose. Don't have a pic handy, but you simply cut the hose and clamp the valve in-line.
I don't seem to have a big heat problem, but I live in Va and drive the car on weekends only. There are many, many threads related to the heat topic, many causes and remedies. There is a very detailed thread active on the tech board right now with great pic's on insulating the trans tunnel etc...
My suggested would be to loop the heater hose at the engine for a quick test. If that eliminates your issue, then thats you fix...else you have to start looking at other potential causes..