Measuring for pushrods w/hydraulic cam?

I would like to know pls. Getting ready to do this for new custom cam.

Figure out roughly ,the push rod length. Order the correct push rod... Comp Cam's ,seems to have a damn nice one(personal experience..).
http://www.google.com/url?sa=t&sour...icQs8wtznW6rQdn3Q&sig2=7kn2jAMBNRYgmcjhhcrgTQ
http://www.google.com/url?sa=t&sour...5ks6IKmVaqv7HJvmw&sig2=4Ywfk8FxMLgHJwppOHgI2g
Watch both,think about it & ask questions.....