Hmm, so many questions but let's have a go.
I can't think of a way to measure displacement without pulling a head off. You need to know the bore and stroke, maybe someone has a way to do this with the head on but I have not heard of it. Cam specs could conceivably be measured like that but my guess is that it would not be super accurate. The dyno can tell you lots of things. Not only how much hp/tq but where it comes in, are the curves flat or linear increase and lots of other stuff you couldn't imagine. A good dyno/tuner can really set up a car. As for damage, it's no more possible than any other spirited driving you might do but I will leave you with this one piece of advice. Don't be there when they do it. You don't want to be around when they wind out your baby to full song. It will make you cringe.
