I need to pick up a new heater hose fitting (The heater hose nipple at the manifold) I'm not sure what size I need to get. I believe it to be 5/8" hose fitting w/ 3/8" NPT thread, but there are 2 styles, one that is slotted to tighten w/ a screwdriver, and one that has a hex lug on it. I don't...