Engine dyno
An engine dyno can be good if you need to break in the cam, then swap in inner valve springs, or when you want to have a good idea of what it can do for power, and when. That's helpful in choosing a convertor set up too. Most dynos around me are well know to performance machine shop owners. Because they will have used them at one point or another. A dyno is only a tool. A big, cool one, but thats' it. The only way to see really what it will do, is accelerate a mass down the 1/4 and see how it does. Also, like flow benches, results are heavily dependant on the place the dyno is, the operator, the exh system and air system in the testing cell, etc. Great tools, nothing more.