NOTICE REGARDING PYROMETER INSTALL. PLEASE REMEMBER THIS.
THE ONLY TIME YOU NEED TO INSTALL THE THERMOCOUPLE PROBE DIRECTLY INTO THE EXHAUST MANIFOLD IS IF THE ENGINE HAS A TURBOCHARGER. ON NORMALLY ASPIRATED ENGINES THE BUNG/THERMOCOUPLE IS INSTALLED IN THE THIN WALLED EXHAUST PIPE. Right behind (downstream) of the exhaust pipes "Y" connection is an excellent location for it. Mine is about 4 inches behind that connection and it was installed by the original Ford Dealership along with the "Banks Power Pack" set up in accordance with BANKS specifications. In 1987 the Banks Power Pack (which includes the Pyrometer) was a Dealer Installed Option. Turbo chargers were introduced the following year, 1988, so the "Power Pack" became obsolete. Specific information & INSTRUCTIONS further below.
I'll explain now why there is a difference in location on the turbocharged engine compared to the normally aspirated engine.
Normally aspirated engine: Hot expanding exhaust gases flow from the manifolds directly into the exhaust pipes at high volume and high velocity. As the RPM increases, the volume, velocity and temperature increases, especially under load like pulling a trailer up a hill.
In this engine there is NOTHING within the exhaust flow path that would interfere with the exhaust gas volume, velocity and temperature other than the resistance of the exhaust pipe inner wall, and NOTHING that would act as a heat sink to significantly lower exhaust gas temperature. So, the location I mentioned, just behind the exhaust "Y" is just fine for the pyrometer probe. IN FACT that is still the BANKS specification to this day for the Ford/Navistar 6.9L/7.3L IDI diesel, naturally aspirated engines. You can read it yourself, further below.

TURBOCHARGED ENGINES. The turbocharger is right in the middle of the exhaust flow. IT CONVERTS HEAT ENERGY from the hot expanding exhaust gases INTO MECHANICAL ENERGY. Relative to exhaust gas temperatures, the turbocharger acts as a huge HEAT SINK, lowering the exhaust gas temperature exiting the turbo by around 300 degrees. That's why the probe needs to be installed before (in front of) the turbocharger and unless the turbo has a special probe installation port already made in the turbocharger at the factory, (Banks turbochargers have them) then you may have to drill into the exhaust manifold.
In selecting location for the hole in the exhaust manifold, don't just 'pin the tail on the donkey' or go by hearsay, but follow manufacturer's specifications. Personally, I would set it up on a good drill press to get an accurate and straight hole, using a good bit at the correct speed and cutting oil. I would want the hole and the tapped threads to be as perfect as I can get them because I know that small defects such as an unintended tiny cut or notch along any edge of a cast iron part when under stress can cause a crack to form. Exhaust manifolds should be checked along the mounting surface for straightness and resurfaced if it's not 'exactly straight.' Otherwise you'll get built up stresses in the cast iron when the manifold is finally torqued down. Shops that specialize on re-building engines or re-building heads know all of this stuff.

FROM THE INSTRUCTION MANUAL:

Instructions for the BANKS DynaFact Pyrometer Gauge:
https://s3.amazonaws.com/assets.bank...o_gauge_v5.pdf