Wasn't criticizing you in the least, but you would get more answers elsewhere (Performance Modifications). But like Gslocum said, I did answer your question. Most of the gauge questions posted here are about lighting and how to change/modify it for aesthetic purposes. But just for shits and giggles here's a longer answer
I have my oil pressure sending unit installed in the side of the head. It's been there for a year and a half with no issues. There is a how-to in the how-to forum posted by someone that tried using a brass fitting to get more clearance when placing the sending unit in that exact location. Every brass fitting (or other fitting) they used, inevitably cracked. The hole is already 1/8NPT so there's no need for adapter fittings for most sending units. But placing anything in there, such as a "T", you are simply asking for it to crack. Especially if you have solid mounts as the vibration is increased with these in the car.
To me...pressure in the head was more important than pressure in the pan. And temperature in the pan would be more important than temp in the head. It would also give a more accurate reading of the temperature the oil actually is before it's picked up and sent throughout the engine. If you do a search on here you'll find many people differ in where to place these sending units for readings. But that's my .02 on the install of them.
*Edit* Use some white teflon tape when installing the plug into the head to prevent it from leaking.
Oil temp and pressure gauge off the plug on the engine block.
Linear Mode
