Its like a ghost hunt isnt it? 1969 and down is a piece of cake. Help Section at any parts store will have a 3/4 NPT by 3/4 heater hose fitting. 1970 and up, not so much.

Ebooger sells them on Ebay. Kinda pricey if you ask me though. I got one from Mcmaster Carr through work. On the cheap you could use a 3/4 NPT piece of pipe and cut it down about an inch past the last thread. The guy at Summit told me he gets request for that quite frequently yet they have done nothing to address the problem.