1974 Duster - First Mopar

On your second picture, if that came off the fender well, down towards the battery, it is most likely the starter relay. Can't be for sure unless we could see the top where all the wires attach.

And if it was a non AC car, it could have had that smaller radiator in it. I had a 71 Duster that was a 318 no frills car (no AC/PS/PB) and it had the smaller of the 2 radiators.