Volvo Repair: engine rebuild, volvo engines, flex plate

Question
I am reinstalling a friend's flex-plate on crankshaft of '84 240 B23F engine with auto transmission.  There are two metallic rivets (1/4" studs, actually)appoximately 2"-3" apart on the plate that line up with a threaded port on the right (passenger) side of the engine block.  The flexplate position was not marked during disassembly.  My suspicions are they are some type of speed reference.  Are these studs used for any purpose?  If so, what is the proper installation position?  What is the name of the sensor that uses these studs, and what system uses the signal?  Thank you.
Melvin  

Answer
On "early" volvo engines, the tester or scope used  for engine diagnostics used a reference sensor indicating TDC which is the studs you are talking about on the flexplate. The connector is mounted on top of the valve cover, and the sensor is mounted on the engine looking from the rear at about 1:00.
This sensor is hardly ever used, don't worry about placement of flexplate.