just to be clear, you want clearance between the power booster and the mc push rod?  or no clearance?  Did you say a 1" gap ???

At rest, (brake pedal NOT applied), the output of the rod should not be making contact with the back of the MC piston.

http://www.maximummotorsports.com/content/install/pdf/brakes/MMBAK-1r1.pdf

The tool I use consists of the end cut off an old master cylinder.  I then welded a 1/4" wide piece of steel across the open end so I can see the booster rod.  I made the steel piece so when the rod is just shy of touching it, then the rod is at the right depth.  I adjust so many boosters I had to have a custom tool. 

I used to use the method shown in ultrastang's link, but that is very cumbersome and there are multiple points of possible error whenever you have several steps to a process and each step requires a human intervention like reading a dial caliper, and positioning it correctly.  Not everyone is even capable of doing that or  might not have the right tool.  (But for $20, you SHOULD have a dial caliper)

The other method I use when on a vehicle and my tool in not available is to adjust the rod too long, until the mc rocks on the longer shaft.  Then carefully back off the adjustment until you no longer can feel the mc rocking on the rod.  It is not as precise as using my calibrated tool, but it works.