This is the hose I ordered from Rock Auto for the upper hose, and I'm pretty sure it's the one I ended up using. (I bought and returned many hoses to Auto zone and Rock Auto).
I searched for the hose for a "1990 CHEVROLET C1500 PICKUP 5.7L 350cid V8" on their site. It's a GATES 21191.
https://www.rockauto.com/en/moreinfo...=1031184&jsn=2