Addison,
I found that problem is easily solved by approximating the radiator hoses you need with anything flexible that will hold its shape, like a welding rod or straightened out coat hanger, and taking those samples to a big, friendly auto parts store. Counter men/women who know you will let you rummage through their radiator hoses until you find molded hoses that are a fit.
I wish I had the computer skills to post a photo of how that worked out in finding hoses for my sbc 350 powered '32 Ford street roadster. The hoses for some other vehicles are a perfect fit in that roadster.
Good luck. You can do it!
This is exactly what I do at O'Reilly's when I have a hybrid engine/radiator situation. One other point is that you may find the shape within the shape of a hose. So get that one and cut it off.
I buy any and all that look close and take back the ones that don't work. I don't use the rubber corrugated flexible hoses. Those are for tractors and engine stands. Never had any trouble finding/modifying a nice Gates hose as Pieman says. There is nothing radical about what you are doing. It's just that every swap is a little different so there is no way of giving you a part number. You have to do some work. It's easy.
Obviously you need to know the ID's you need on each end.
