Retro fitted 2 74 cars,a Charger and a Challenger.
Both had baked electrical systems and it was easier to install a complete used 72 or 73 dash and underhood harnesses .
I do continuity tests on all circuits,repair any wiries as needed and retro fit an electronic ignition harness if i use a 72 harness. Also good time to clean all of the spades in the bulkhead connector
I re-wrap the harnesses for a clean appearance.
I always bypass the ammeter gauge at the same time.
I did not bother plugging in the relays for the buzzers and left the seat sensors alone--nobody sees them anyways.
Hope this helps