thats for the oe combination oil sender switch (for idiot lamp) and fuel pump secondary
most delete the sender when adding an oil pressure gauge
if you arent running a sender cut the wires off and tape them up .
if the contacts in that plug contact metal you can blow the Fuel pump fuse and that will kill the pump and leave you stranded if you dont know how to repair . from the looks of the plug youll be needing a new connector any way so cut it off now and if you decide at a future date you'd like to reinstall the sender you can get one from caspers electronics
Might want to go completely through that car .. oil, plugs, wires, vacuum lines , fuel , filters blah blah blah ... that engine doesn't look like its run in a while