Help with 1975 Duster ID

thanks,

We are starting with this new hobbie, not even a year. We hace a Chevelle 67, a Mustang 65 (my baby) and this Duster is only been home for a week or so. In Puerto Rico Mopar cars are rare, and in good conditions even more. Some people tell us that it wasnt a good buy because is a six in line but we like it, and is solid, no rust, and has its lines. He is giving it a good makeover (rug, a good cleaning, painting the trunk, new interior panels,) .
I like to look for all the original car info, even thou that he will probably change it to what he really likes. For example, we will put the black lines at the sides.

So, any aditional info I will apreciate it. Ill post more pictures tonight