Bought my first mopar 73’ Duster and the bottom of the air filter pan is black (right above the carb). Any tips on how the 4bbl should be adjusted

One of the "other" first things I'd want is to try and backtrack some of the car history and find out what is "in" the engine.......has it been bored, higher compression pistons, any head work, and what cam is it it and "has the cam been degreed?" After that I'd graph the timing of the distributor and if necessary see about recurving it.

When it idles is it your impression it has a "hot" cam? But you only want to evaluate that if you know it is in good condition, tuned, and running well, as engine problems can "make it seem" so

That looks pretty nice. You should have a lot of fun with it.