Cam identification how-to??

What's the easiest way to identify a camshaft with the engine installed and the intake off??

I was told the cam in my 340 was a MP one. I know it's a hydraulic flat tappet. I'm guessing either the 280* or 284*.

I'm going to install a new intake this weekend. Can I losen up one of the rocker shafts and put a dial indicator on one of the lifters to measure the lift, or will the lifter bleed out enough to screw up the reading?

Thanks for your help.