You will have to find your oil pressure sending unit, remove it and run the plumbing from there. If you can't fing the sending unit let me know and I will look it up in my Bently manual. The sending unit will normally be on the block near the oil gallery next to the oil pump or on the aft end of the block at the end of the gallery. If you find it, remove it...oil good, antifreeze bad. If there is antifreeze it is your water temp sending unit, try again. Good luck.
Not sure if this helps or not, but go to 42draftdesigns.com and check out their directions for installing a oil pressure guage. They have a great diagram of where THEIR sender goes (right on top of the oil filter/cooler assembly there is a plug you can remove and replace with the sender). I have no idea what guage you purchased or whether your sender will fit in this hole, but worth a shot.
I've been through all this getting my VDO's all setup.
Do not remove your stock oil pressure sending unit. You will have a gauge that works and an idiot light that stays on.
There is another unused tap on the block above the oil filter. You can attach your aftermarket pressure sending unit there. If you want to attach more than one addtional oil unit, like temperature, you can get an extension and adpater from 42dd that connects to that new block tap location and allows 2 senders to feed off one tap. Do NOT use this extension for oil tempertaure. The straight extension tube will not circulate oil so the temp sensor will read low by a HUGE amount. Trust me. The heat does transfer up the extension tube and I've spoke with 42dd about this and they confirmed that as well.
If you want oil temp as well as pressure, you will need to remove the stock pressure and place the aftermarket temp sensor on location. Then place the stock and aftermarket pressure sensors on the 42dd remote extension kit at the 2nd tap location.