Upper being one designed to hold pressure and not vacuum as the lower is the suction side of the system. Gates state they have designed into their hoses with a fiber braid to prevent collapsing, but is that across the board or specific hoses??

If you don't have a spring on hand, there is a Mustang parts guy (CJ Pony Parts) that sells a stainless lower rad hose spring for under $10.

Might as well as try and eliminate the easier and lower cost items to make sure your foundation is solid before jumping into the $$$$ items.