Ron, You should be able to find them at a good auto parts store or a hardware store. You will need the "T" (1/8" NPT) and a Close Nipple (1/8" NPT X 1") to screw the T into the block. You can then put one sensor (or Oil line) in each end.
Magnus, I would agree with Rob that you keep the light if possible as it will get your attention much faster than a gauge will if there is a problem. We still run a light on the race cars along with an engine shut off, it alwways gets the drivers attention fast.
You should try to mount your new sending in the rear with the "T" method suggested if possible to keep it out of harms way and make the installation look nicer.
Yes, the oil pressure in the readings for the engine should be about the same no matter which tap you use.
As a PS: You could use BPT fittings available in Europe if you need to. They are just about the same thread size but they do not have the "taper" that NPT fittings do. I have used them on several occations when I couldn't find NPT fittings over there. They will not screw in as far so be aware of this.