Heads milled

I picked up a few small block parts off a friend of mine.
In the parts there was two sets of "J" heads.

One set looks untouched, the other set has been milled alot, they look like close chamber heads, there was so much taken off them.
What is the easiest way to determine how much these heads were milled?
He cannot remember how much he had machined off of them.

Also I have an intake that I acquired that I know has been milled, but do not know how much, how do I measure it?