Hello 2ton46, Nice truck and your "Brownie" does shift very nice. Did you complete the install yourself? My GMC is very similar to your truck but I do have PTO and a dump box as well as a short wheelbase. I envision mounting my Brownie at the midship bearing frame bracket and take my measurements from that point. I had read that you do want some U-joint deflection as no deflection is bad and will wear our your U-joint faster. My dump control levers are currently located right in front of the gas pedal (not so good). I plan to move them to the right of the main box shift tower, the aux shifter positioned like yours. Do you have a 2 speed rear end?
Al
Alan