1972 Duster factory electronic ignition harness into a 1971 Duster 340 (rallye dash)?

The above. I think the big thing is translating the wiring your new harness has AT THE CLUSTER connector to the Ralley dash. The connector(s) may not even be the same.

the manuals, generally, do not detail the cluster inner workings. But if you can post clear shots of the clusters we/ you can SEE the traces. The way to do that is to not try and post just one shot. Get overlapping closeups an and post one cluster in two shots. Also need to reference the rear of the cluster to function, so post a shot of the front as well.