Rotor Question
 

I know its a dumb question... I am doing the 73-87 frontend swap on my 65 C10. When I measure a 73-87 rotor, am I measuring the thinkness of the rotor at the braking surfaces or from the edge of the wheel flange to the braking surface? Also, I bought a set of spindles from craigslist, and I am not sure which rotor they are designed for, does anyone have measurements so I could tell which ones they are?

Thanks In Advance!