@Rick76
Thank you so much! That is EXTREMELY helpful! Really appreciate you taking the time to write all of that down. I will go trace some wires this weekend!
@Funola
So, my research combined with what Rick76 is saying means the following:
1) All W123's up to '84 use the tach amp
2) Early Federal 84's use pick-up directly to cluster, but
all California 84's have signal through the EGR controller with the OVP under the passenger kick panel as do most/all late 84's
3) 85's are the same as late '84's, and use EGR controller, both Federal and Californian
My car is early '84, so apparently it's the weird setup directly into the cluster (although I haven't checked or traced any wires yet), but what Rick76 is saying matches perfectly with what I've found so far.
@DeliveryValve
Thanks bud!
You guys rock.