having gone through this with my 88 recently, i'd suggest that it is
most likely the $15 high pressure oil switch. it's hidden down in there,
beside (left side) of the main pulley, below the water pump.

and, yes, it gets oil all over the bottom of the engine!! beats me how,
cause i was chasing the leak all over the place, thinking it was push rod
tube seals, then main seals, etc. finally i got a couple of cans of brake
cleaner and cleaned the entire bottom of the engine, and just watched to
see where it was coming from ... and there is was.

and it is a royal bitch to change!! :(

figure a dealer will change about $20-25 for the part, and another hour
of labor, $50, for the work (and in this case, i think it's worth it!!)
so figure $75 total. :(

joel