Looks like a magnet for helicopters.
Definately not aftermarket ( it actually has the Pentastar and part #). I have it in my Duster. The Duster is a 72, however the harness is from a 74. No seatbelts hooked up and starts fine. Don't believe it's a seatbelt thing. Could be wrong but mine starts fine without seatbelts hooked up.
here is a google picture.. maybe it is factory. no idea what its for though.. check out the service manual.. maybe that will tell ya.
You sir, are correct. I wuz wrong. Did some digging today....EGR time delay module.
The seat belt interlock system introduce in 1973 or 74 isn't related and is on the left side as Abodyjoe is indicating.