Lulzbot TAZ 5 mount for a digital indicator, such as the Mitutoyo 543-253. Used extruder model directly from Lulzbot and modified to allow for a digital/dial indicator with a 0.25" thick mounting lug and at least 0.5" travel. I used a 1/4" diameter shoulder screw and external-tooth lock-nut to attach the indicator to the mount. I opted for the shoulder screw mainly to save the finish on the lug of the indicator -- I also had them on hand.
I removed the extruder head completely from the printer, and as a result had to connect a resistor across the two thermistor pins on the printer harness -- otherwise a "Min-Temp" error would come up. I do not recommend completely removing the extruder if you're not comfortable with inserting the resistor on the thermistor pins, and I am not responsible if you short the wrong pins.
McMaster-Carr Hardware used:
90675A011: Steel Locknut with External-Tooth Lock Washer Zinc-Plated, 10-24 Thread Size
91259A537: Alloy Steel Shoulder Screw 1/4" Diameter 1/2" Long Shoulder, 10-24 Thread