1970Ford Mustang

Cowl / plenum (under the windscreen)Critical

The classic first-generation killer. The cowl vent drains block with leaves, water sits in the plenum, and it rots from the inside out — invisible from above. Run a hose into the cowl vents with the doors open and watch the footwells and the kick panels. Wet carpet after rain, or a heater that smells damp, is the tell.

Repairing a rotten cowl means removing the windscreen and cutting the top off the plenum. It is one of the most expensive rust jobs on the car and it is routinely hidden by a fresh carpet set.

Torque boxesCritical

Structural boxes tying the floor to the frame rails, behind the front wheels and ahead of the rear wheels. Convertibles have extra ones and rely on them completely. Get underneath and prod them. Doors that drop, or that need lifting to latch, point straight here.

Convertibles have no roof structure, so rotten torque boxes let the whole shell flex. Treat this as structural on any open car.

Front shock towersCritical

Check around the upper shock mount and where the tower meets the inner apron, on both sides. Cracks and rust here change the front suspension geometry and are a safety issue, not a cosmetic one.

Rear frame rails and spring perchesCritical

Follow the rails from the torque boxes back over the axle. Rot at the leaf-spring front hangers is both common and structural.

Floor pans and toe boardsMajor

Lift the carpet — all of it, both sides, front and rear — and look from underneath as well. Patches welded over patches are common. Fresh underseal on an older car is often there to hide something.

Rear quarter panels and wheel archesMajor

The most visible rust and the most frequently bodged. Check inside the boot, the drop-offs either side of the boot floor, and behind the rear wheels. A magnet finds filler; a torch inside the boot finds daylight.

Boot (trunk) floor and drop-offsMajor

Lift the mat and the spare. Water enters past perished rear window and boot seals and collects here. The drop-off panels either side are a known rot point and are structural on convertibles.

Lower doors, front fender bottoms and rear valanceModerate

Drain holes clog and the panels rot from inside. These are bolt-on or readily available panels, so they are the least alarming rust on the list — but they signal how the car has been stored.

Panel gaps and door fitCritical

Stand back and look down each side. Uneven gaps, a door that drops on opening, or a bonnet that sits proud usually mean structural rust or an old accident — not a bad panel fit from the factory.

VIN, door data plate and paperwork agreementCritical

Check that the VIN, the door data plate and the title agree with each other and with what the car actually is. A car sold as a GT, a K-code or a Pony-interior car should be verifiable from its codes — and codes can be, and are, faked.

Codes record what Ford built, not what is in front of you now. For a car with a significant price premium riding on its identity, get a marque registry or a specialist to look before you pay for the badge.

BrakesMajor

Four-wheel drums were standard; front discs were optional on V8 cars. Establish which the car actually has before buying parts — and expect drum-braked stopping distances if it has drums.

Charging and wiringMajor

Original harnesses are sixty years old. Look for added inline fuses, spliced repairs and aftermarket accessories wired straight to the battery — a genuine fire risk on a car with fabric-loom wiring.

Fuel system after long storageMajor

Tanks rust internally and modern ethanol-blended fuel attacks period rubber. A car that has stood for years usually needs the tank, lines and flexible hoses done before it is safe to drive far.

Convertible top, frame and sealsMajor

On an open car, check the frame for rust and the mechanism for operation under its own power, plus the rear window and the seals. Also confirm the extra convertible bracing underneath is present and sound.

Evidence over descriptionMajor

Ask for receipts, photographs of the car mid-restoration, and a look at it on a lift. A seller who can show the bodywork before the paint went on is telling you more than any description.

Engine — 200 six / 289 V8Moderate

Both are tough, simple and superbly supported by the parts industry. Look for oil pressure once warm, smoke on the overrun (valve seals) or under load (rings), and coolant in the oil. A tired one is a known-cost rebuild rather than a deal-breaker.

Front suspension and steeringModerate

Upper and lower ball joints, idler arm and the steering box all wear. Excessive play at the wheel and a wandering front end are normal for a neglected car and are a well-trodden, affordable rebuild.

Cooling systemModerate

These engines are not prone to overheating when healthy. A car that runs hot in traffic normally has a silted radiator, a tired water pump or a missing fan shroud — check the shroud is actually there.

Interior trim and glassModerate

Reproduction upholstery, carpet and weatherstrip are cheap and excellent. Correct original trim, date-coded glass and undamaged dash pads are not — and they are what separates a good car from an average one.

Non-original drivetrainModerate

Engine swaps, later five-speeds and disc-brake conversions are extremely common. None is a fault — a modified car can be the better driver — but it materially changes value, so establish what is actually fitted rather than what the advert says.