Ok, for anyone keeping score, I picked up a P4510640 Adjustable Master Cylinder Pushrod Package and its specs are:

Fully screwed in, from the tip of the ball end to the center of the bolt hole is 7 1/16".

Unscrewed as far as I would take it (about 3 threads engaged), it's 7 15/16" in length.

So it looks like it should work just fine as Scratch said the factory piece is 7".