1970-1975 Gold Duster Option:
Tag has the A64 option (I think).
Should have a 'snakeskin' vinyl roof (All of them I've seen are 'canopy' or half roof type), cigar lighter, could be a 225 or 318 optioned car, wheel covers, usually came with the 'chrome/bright' package (drip rails, wheel lip mouldings), 'Gold Duster' sticker on each front fender, Tape stripe on the body, etc...
1976 Feather Duster:
A31 Fender Tag option code.
aluminum bracing/webbing under the hood and trunk lid (some units didn't get an aluminum hood/or trunk lid as factory supplies got spotty), the reinforcement behind the front and rear bumpers are cast aluminum, the intake manifold is a cast aluminum 1 barrel unit, aluminum bellhousing and tranny case if optioned with the A-833 OD manual tranny, with mandatory 2.94:1 7 1/4" rear end (2.76:1 if optioned with the A904 auto), Disk Brakes, 'Feather Duster' sticker on the front fenders, Mandatory 225 /6, with economy curved distributor (not shared with any other 225 equipped that year), and special EGR (only optioned for that car). I've seen them equipped with: sunroof(rare), A/C, canopy vinyl top only, bucket seats, Spacemaker fold down rear seat, smog pump, and I've heard some of the 'earliest' ones had been equipped with 9" drums and an A-230 3 spd manual (like the one's that rolled out in August or early Sept.)
1976 Silver Duster:(replaced Gold Duster)
Option Code A62
Special Tape stripe, Red/Maroon Velour interior(has some gray and white stripes), Silver exterior pain,the rest of the mandtory options are not known they aren't common outside of pictures in catalogs.
Duster Twister:1972-1975(?)
This is Plymouth's attempt to 'provide' a sheep in wolf's clothing. It has all the options one of the 'muscle' cars would have: Rallye Wheels, good brakes, tape stripes, rallye dash, etc...but can only be optioned with a /6 or a 318-2v (a Duster that looks cool, but insurance companies won't crucify you for owning it...)
There was also the Duster '340' (1970-1973)and Duster '360'(1974-1975, in 1976 you could option the duster with a 360, but it wasn't badged as a 'Duster 360'....)...
There are some sites with more or less info, just do a search for 'Plymouth Duster' and there are several pages dedicated to the Duster, and her sister cars, the Dodge Demon(1971-1972), and Dodge Dart Sport(1973-1976)....
That should tickle you curiousity,
-D.Idiot