Welcome! That’s a clean Duster and great to see another ‘75 A body around!
There is a service manual book which includes wiring diagrams for the ‘75 cars. There’s another Mopar website that has the service manuals for most (all?) of the years so try googling it. They have been scanned into pdf format.
Here‘s a hard copy I picked up at a swap meet a couple of decades ago for my ‘75 Scamp.
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