I think you were supposed to pull the spring out of the old hose and put it into the new one. But since these cars are 40 or so years old, the hoses have been replaced several times and the spring got thrown out with the old hose at some point in time.
I think it would be pretty easy to make a new spring out of some 1/8" aluminum wire. Just wind it around a broom handle or something similar. I know my lower hose has no spring inside it, and my 340 runs kind of hot. The spring might just be the answer, as I've done everything else.