You don't need to drill and tap anything, you need an 1/8" BSPT (British standard pipe thread) tee, you will then attach the stock oil pressure sensor to the tee, and to the other port you will install your fitting, which will probably be an 1/8" npt to a #2 or #3 AN 37 degree fitting.

You can also use just plain NPT fittings, but since the thread is slightly different you will have to use teflon tape and really bury the fitting - not recommended but an option.

Don't forget the oil drain. Your boss will need to weld a #10 AN fitting into the oil pan for a drain. Or buy a Moroso oil pan with a bung for an oil drain fitting already on it..

Last time I checked, Z10 engineering was selling 1/8 BSPT fittings, check out their website, or search your local hardware stores. Good luck. And ask your boss why he is buying a high compression JDM motor just to turbo it...If I was starting a project with the intent of turbocharging it that would not be my choice of motors. Start with a lower compression motor, and build it for boost....but whatever floats his boat...