Ok so I did some resistance testing, results were as follows:

NC to NO = 1
C to NC = 000
C to NO = 1
Switch housing to frame = 001

I also did some other testing:

With ignition wire (86)(yellow) disconnected from C on the oil switch, there is no power to the purple (87) or yellow (86) wires at the relay. Not even when cranking. Nor is the fuel pump kicking on.

When I attach 86 to C the pump turns on, and 87 and 86 get power at the relay.

When 86 is disconnected from the oil switch NC and C have power when the key is off.

When the key is on, all three terminals on the switch have power, C, NC, and NO.

All this said, it didn't lead me to any conclusions, but I'm no electrician either. Does this lead anyone to a conclusions?