1973 Plymouth Duster with a 440 swap, narrowed 8 3/4 Sure Grip and fresh tune-up

Why we picked it

Why we picked it: this Duster started as a slant-six car and now has a 440 with a rebuilt Holley, new fuel pump, alternator, distributor and ignition parts, backed by a TorqueFlite and a rebuilt, narrowed 8 3/4 rear with Sure Grip and 3.55 gears. The seller also lists a 1 3/4-inch front sway bar, brake service, new 15-inch US Mags with BFGoodrich tires (the old Cragars are included) and a clear Kansas title.

Modified small- and big-block Dusters have been selling for $20,000 to $33,000, and this private-party car is asking $19,500 or best offer. It is a driver, not a show car: the seller mentions roof peeling and paint chips. That makes it a good base to sort and drive while you plan paint and chassis upgrades.

The value check

The seller is asking $19,500. Comparable cars in the same condition have sold for $20,000–$33,000, so the middle of the market is about $26,500. That put this car 26% under.

Modified, engine-swapped Duster drivers sold between about $20,000 and $33,000 in the last year (for example $20,900 at Barrett-Jackson and $24,200 at Mecum in Sep 2026, and $30,800 and $33,000 earlier in 2026). Asking $19,500 OBO from a private seller.

Where the numbers come from:

• 1973 Duster, swapped, Mecum Sep 2026, $24,200
• 1972 Duster, 383 swap, Barrett-Jackson Sep 2026, $20,900
• 1970 Duster, modified, BaT May 2026, $20,000
• 1970 Duster, custom, BaT Aug 2026, $33,000
• classic.com Duster sold results

What to check

• Check the rear frame rails, trunk floor, lower quarters and the area under the rear window for rust, all common A-body trouble spots
• A 440 in an A-body needs the right K-member, motor mounts and headers; ask what was used and look for steering box clearance problems
• Torsion bars, front brakes and cooling were sized for a slant six; confirm what was upgraded
• Factory A/C is disconnected; the dash pad needs replacing
• True mileage is unknown; the listing does not give a date, so confirm the car is still available

Making it drive like new

Start with brakes and suspension: bigger torsion bars, front disc brakes and a quick-ratio steering box (or rack conversion) to match the big-block weight. Add a modern aluminum radiator, an overdrive automatic and subframe connectors to stiffen the unibody.

1 builder makes a complete chassis for the 1967–76 Mopar A-body (Dart, Duster, Barracuda, Valiant). Compare them side by side, along with what it takes to stiffen the factory frame.