273 valvetrain question

Well, you kindof need to know those things to build a successful combo, the heart of which is the cam.There is no sense putting a 6000rpm cam into as 5000rpm combo.And especially into a completely unknown combo.
The operating range of the engine, more or less dictated by the cam,is usually selected before the engine ever goes together, and then, the rest of the combo is built around it.
But in your case, the combo already exists, so, now, the cam has to be chosen to make it the best that it can be.To do otherwise, invites a re-engineering of the combo, which usually leads to a lot of money being spent.