I have an oil pressure meter I need to install for my 03 Disco. Not worried about the wiring but not sure how or where to install the oil pressure meter to touch the oil.
Pictures do justice so here we go.
If we can figure this out, then I am 3 steps away from having my dream truck on the road......

 

You should have got a oil filter adapter from glowshift or something. Now your going to have to tee of somewhere to plug that in.

 

There is a plug for the oil cooler return line connection, but there is no cooler on the '03. It is before the filter (pressure drop), but after the filter is very complicated to install.
Ignore the AN-fitting (this was just an experiment). The thread is M20x1.5:

 

Yeah, that plug location is the one to use. You can get an aluminum plug with mating threads at the auto parts store and drill and tap it for the pipe threads.