Hi Harold,

Good observations.

From my experience, the round plug was used with both Chrysler (white cap) distributors and Bosch. I've only seen the round plugs on 83 and earlier, but mated to both orange and white cap units.

The Hall sensors are themselves all the same. The three different assemblies provide mounting to accommodate the geometry of the distributors they fit; Chrysler, and the two (thick and thin) Bosch. Actually, I think there may be 4 assemblies available, because two of the Bosch have the same fit but come with either round or rectangular connectors. Apparently the round-plugged Bosch is rarer than I thought.

I'm certain the drive gear and i-shaft mate identically in all models.

I haven't proved it with experience (or this thread would be much shorter) but believe the only difference in the Hall-type distributor part numbers going from 84 on is due to the beefier shaft. A Hall-effect switch is a simple device that only reports whether the trigger wheel's vane is blocking or not blocking the magnetic path. That's why I posed the yet-unanswered question regarding a possible difference between vane window ratios. If Volvo changed that, it would require a matching change in the ignition computer.
--
Art Benstein near Baltimore

Always remember that you're unique. Just like everyone else.