I just stumbled upon this online performance parts place http://www.pricemotorsport.com/ and they make adapters for a number of different engines that allow you to use various intakes with various blocks and various heads.
I looked at there listing for adapters for my application so I could use a 302 intake on my 351w. They are like 250 so it's a moot point for me, but for someone who's already got a high flow 302 intake and wants to upgrade to the 5.7L then you could get a set of these things and reuse that 302 intake.
I've seen those, my buddy has a Parker Funnel Web that might benefit from some adapters to go onto a 351w based engine as I don't believe they make a 351w baased intake.
For the price of the adapters and an intake you could buy an intake that fit. But, for instances where an intake doesn't exist for a 351w, like a 2x4 high rise tunnel ram, it would be great.