Drilled, reamed, and tapped the 1/2 NPT hole for the oil temperature sensor adapter. Unfortunately, R.S.Hoover doesn't give instructions on how deep to run the reamer or the tap, so I only opened up to the begining of the oil pump feed hole with the drill bit then switched to the tapered reamer. I went 720 degrees at a time then reversed and vacuumed out the chips. I kept going until I had a cut fresh metal for the full taper which ended up being almost to the end of the oil pump feed hole. I decided to keep going three more turns and have the 45 degree taper at the end of the reamer help the oil "turn the corner" into the oil pump feed hole. I then switched to the 1/2 NPT tap and repeated the procedure going 1/2 turn at a time until I had four threads showing. This ended up being just shy of the oil pump feed hole. I will wait to add any more until after the 1/2 NPT plug arrives so I can check how deep it seats. Below excerpt from https://bobhooversblog.blogspot.com/2006/12/vw-pulling-plug.html - - - - - - - - - - - - - - - - - ** - Volkswagen provided oil temperature and oil pressure gauges on some of their industrial engines. The oil temperature sensor was placed at the inlet to the oil pump. Early model crankcases had a threaded hole (M16x1.5) at that location. To install the sensor the threaded plug was replaced by the matching VDO temperature sensor. On later model cases the hole is no longer threaded and is sealed by a Welch plug about 19mm in diameter . To install the temperature sensor, pull the plug and thread the hole to accept a suitable adapter. Be sure the temperature sensor extends far enough to be constantly bathed by the oil being drawn from the sump but not so far as to obstruct the flow. On most late model crankcases, a half-inch NPT hex-head plug, drilled and tapped to accept the temperature sensor, makes a suitable adapter. - - - - - - - - - - - - - - - - - - - - - - - - - - - Specific instructions at https://bobhooversblog.blogspot.com/2007/06/help-more-on-plugs.html I settled on an AEM 30-2012 sensor vs the GM CLT sensor. Double the cost but the AEM offers a bespoke data sheet with calibration curve data, higher measuring range (200*C vs. 150*C) and is both smaller and lighter being 1/8 NPT instead of the GM's 3/8 NPT. http://www.aemelectronics.com/files/instructions/30-2012%20Sensor%20Data.pdf