Rust Busters begins with the seat pans by drilling out the spot welds.Along the transmission tunnel, conventional welds are ground clear. Spotwelds have to be drilled out carefully, which separates the pans.
Rust has been a problem for Mustangs for as long as there have beenMustangs. Just several months after the Mustang was introduced in 1964,a Ford Technical Service Bulletin was issued to notify dealers aboutpossible cowl-vent leakage and a fast service department fix. Still,cowl vents leaked all over the carpeting anyway, causing seriousfloorpan and kick-panel rust-through. This has been the lament ofclassic Mustang enthusiasts for at least the last 20 years.
Mustang rustdoesn't stop at the floorpans. Trunk areas are another problem areabecause rear-window and trunk-lid seals leaked as much as the cowlvents, causing quarter-panel and wheelhouse rust-through. Frontframerails and inner fender aprons are yet another corrosion problembecause Ford didn't always galvanize these areas. It certainly didn'tE-coat them either, since the first E-coated ones were the '74 MustangIIs, which were completely dipped in an electrostatic primer processthat not only allowed primer to flow into hidden areas, it also promotedgood adhesion with the steel.
This shows just what a throwaway car Mustangs were 40 years ago.Absolutely no corrosion prevention here--just raw steel that was neverprimed or painted. Note the stamped opening in the seat pan of Art'searly production '64 1/2 hardtop. This went away later in production.
Art Cairo is a longtime Ford engineer whohas been with the company since the '70s. In 1974, he found a RavenBlack '641/2 Mustang hardtop in the Detroit classifieds for well under$1,000. The ad said, "Owned by the Ford family..." Because Art isfascinated with the Ford family, he purchased the car. Its serialnumber, 5F07K100148, indicates a low serial number K-car with theoriginal 289 High Performance engine beneath the hood. Art knew the carwas significant to Ford history.
During a Mustang Monthly interview in1983, Edsel Ford II confirmed that the black hardtop had been hisfather's car. It was assembled at Dearborn and shipped to Ford Designbefore it was delivered to Henry Ford II. We'll likely never know howoften Mr. Ford drove this car, nor how interested in it he was at thetime. But we do know this Mustang, possibly the first production MustangK-car ever produced, was worth saving.
Last winter, Art concluded hisMustang needed to be restored to its original rust-free condition, so hetook it to Rust Busters Classic Automotive Restoration in Redford,Michigan, for an evaluation. The body was severely rusted out from theharsh Michigan climate despite being stored inside a garage. By moststandards, Art's Mustang was a total loss. Even though it looked sharpon the surface, it badly needed a full-scale restoration, includingreplacement of the floorpans, trunk floors, and rear framerails.
Whilethe majority of our readers possess neither the equipment nor the skillsto replace sheetmetal, this article will give you some knowledge aboutthe procedures involved when you're selecting or talking with your bodyrepairman.
Rust Busters begins the process of cutting out the floorpan along thetransmission tunnel. The pan is carefully cut as close to the seams aspossible. The objective should always be to follow the factory seams. | 
The main floorpan is cut out in pieces. | 
Expect more surprises underneath the floorpans. Rust Busters separatesthe floorpan from the front framerail extension. They learned quicklythat both front framerails had to be replaced as well. |
With all of the floorpan cut out, it's easy to see how a Mustangunit-body is put together. With hardtops and fastbacks, there isn't muchthere. Note the front framerail extension, which ties the frontframerail to the floorpan. | 
The front framerail extensions were filled with a mountain of rustparticles. They'll be replaced as a separate how-to article in MustangMonthly at a later date. | 
What's left of the main floorpan is peeled away from the rocker panel.Some patchwork rust repair will be necessary. |
The rear torque boxes are separated and opened like this. The easiestway is to drill out the spot-welds, then nail it with an impact chisellike this. | 
Rust Busters uses a straightedge to cut and trim the transmissiontunnel for the new sheetmetal. There's a lot of work to do here. | 
Mating surfaces are cleaned up and readied for the installation ofnew metal from National Parts Depot. |