LS1 Waterpump on GMT800
Every engine swap I do starts there. then I find the hose or two that are the closest. I used to have a contact at Gates to get the actual hose drawings, however that was 2 decades ago.
You may have to buy a weird shaped hose to get what you need ID wise and cut it as needed.
In lieu of that they make alum splices so you can join two different ID or shape hoses.









