will 73 74 and 75 dusters have interchangeable parts that work with each other?

That's a loaded question as there were evolutionary changes to the design each of those years.

For the most part yes, glass is the same, body panels are the same, doors, hood, front fenders(as long as they have or don't have the top mounted turn signals per your project). Motors, K-members, Transmissions, Rear Axles, suspension and brakes can all interchange but only match up certain ways (no 360 in front of that slant six A-904). Shift linkages and clutch linkages will depend also on the equipment V-8/slant-6. Driveline also depends on rear axle, slip yoke depends on transmission.

Obviously the grill also is by generation 1973-1974 being similar, 1975 and 1976 are the same grille, but in 1975 they have clear turn signal lenses with amber bulbs, and the 1976 has amber lenses with clear bulbs.

Interiors will interchange but seat belt configuration changed with optional lock on shoulder belt in 1973, the full shoulder loop belt in 1974 (with bad counterweight lock system), 1975-1976 has the better shoulder loop system with less malfunctions but the placement of the retractor is different than 1974, also the buckles differ 1973, 1974, and 1975/76.

Wiring harnesses changed each year 1973 being an upgraded harness but with the fuse block like 1972, 1974 using the newer fuse block but with 3 clusters of wiring through the fire wall, 1975 starts the catalytic years, so one harness is separated out from the 3 blocks, 1976 is the last refinement with 3 harnesses and 2 auxiliary plugs (1 for windsheild wiper, the other for the transmission hookups- and these are different between manual and automatic trans). 1976 Also has the shunt wiring harness so the full load of the alternator does not go through the amm gauge in the dash, and the car will run if the amm gauge dies...

You can install any full harness from one year to the other, but make sure you know the year and have the diagram as the fuses and equipment they serve changed between the years somewhat.

Instrument panels all interchange but again somethings will be different, 1976 will have a different circuit board and amm gauge than the 1973-1975, also the 1975-1976 cluster will be out of place in the 1973 and 1974 as they have the check EGR light next to the "seat belt light".

Bezels, taillights, marker lights all interchange.

Likewise there are many other items that can also be gotten from the 1967-1972 cars since they are almost the same body in most respects, also the 1973-1976 Dart Sport is the sister car and can be scavenged for parts as well except for the front clip and bumper.

-D.Idiot

thanks for the details