Looking into adding an oil pressure gauge, and I need to figure out what I currently have. Is there a trick to identify one of these? I don't see any markings on it.. Also, anyone know the thread size that holds the clamp down? I think i need a longer bolt or use a nut on the backside...

Looks like a 2 pole VDO sender. Probably 0-80 Lbs. Clean the dirt off where it screws into the hose. If it says 1-5 bar it will be the 80 lb one. 0-10 Bar is for the 150 lbs gauge. Red green wire for the dash light warning. Other wire to the gauge.

Dang, what a newb move on my part. I wiped the grease away, and sure enough I got a 0-10 bar sender. These engine expect to make 150psi of oil pressure???

Not even close to that.

the sender needs to be matched to the gauge. what is the range of the gauge?

If you are running a 911 style VDO insert in your combo gauge you have the right sender, if you are running a stock centre console 52mm VDO gauge you need the 1-5 bar sender .
There are 3 types of vdo 2 wire sensors,2 types are considered 2 pole and the third type takes an earth from the second wire, this is the one you should be using because you have no ground through the rubber oil hose you have,or in your case someone may have used the bracket to ground the sender to the motor so you need to get that back on.
You could check one of your wires is to ground (earth),if so that is correct for your application.
I like to match same brand sender and gauge,but more importantly they must have matching values,good luck.

I currently don't have an oil pressure gauge, so looks like i'll just buy a 0-80psi gauge with new sender. Next is to trace out that extra wire...hopefully it goes to my blank hole in my center console. I checked with my DMM and the sender is grounded with its mounting bracket.