For the 200 the only way to do this is to buy a Greddy Filter extension, which has 1 port for oil temp and 1 for oil pressure, they also do a sump plug with a port aswell (only around £15 to £25), I pressume they (or some1 similar) should do something for the RB.
I tee'd into the block, where the Nissan sender is, to left and below the oil filter, to put in a analogue oil gauge. I put the Nissan sender back on the other side of the tee but see no reason why that could not be, with the right pocket, a temp probe... picture of the tee HERE
I have a suitable tap, to rent , for the block to suit the easily available 1/8" BSP tee's and fittings, full story of oil gauge fitting HERE
RonS - I don't know the layout of all things Skyline so I could not make out the exact layout from your pictures.
Forgive me if you've got all of this in hand but remember that to measure oil temperature, you need to have the probe in flowing oil, not in a static pocket of it? Static is fine for measuring pressure but temperature readings would lag behind actual temperatures and may not be particularly accurace if there is no flow through.
Again, forgive me if you've got this all in hand but I wasn't sure exactly how you intended to do it.
Good point indeed, the oil pressure point shown is a 'dead end' and as you say to get a reliable temp reading it may need to be in the flow, as I had only done this mod on mine for an oil pressure gauge I did not consider that, so I think Si better scrap that idea, back to the drawing board I think