Dennis I appreciate your advice, I am installing a new set of gears, and I bought complete set with new carrier, bearings and install kit. the tool I am talking about sounds similar to what you are referencing. I included a pic

sounds just like I was hoping that after making a dummy bearing and using the tool to determine the proper pinion depth the majority of the work will be determining the carrier shimming to get the proper backlash. Sounds like the real PITA would have been trying to determine pinion depth with trial and error. The tool is available for all different rearends I bought the one specific for the 8.5. You can see from pic the idea is the round side rests in carrier race then measure from the pointed end to the pinion face