well the one that is plugged in, is the water separator bowl heater. The other one may be the low oil level circuit, which lights a lamp in the idiot panel below the low oil pressure idiot light(looks like it has a weather plug in it). they put the low oil level circuit in the A0 wiring harness and idiot panel but did not put in a level sensor for it...
Straight down below that area at the bottom of the block is a small oil pressure manifold tapped off the oil gallery. it has the electric oil gauge sender and the 15PSI low oil pressure switch which should have harness connections...