Transmissions swap

You'll need the pedals, clutch linkage, pivots, NSS, bellhousing, flywheel, trans, driveshaft, shift linkage to start with; plus transmission tunnel hump & boot and carpet if floor shift, steering column if column shift. If floor shift, and if you have a bench seat, you may have to switch to buckets or modify the shift handle. If the parts car is 111" wheelbase, you'll need to locate a different manual trans driveshaft to fit your 108" Duster.
Don't forget that your crankshaft may or may not be drilled for a pilot bearing.
Hell, just grab the whole car.