Problem Child: Dennis Rostenbach’s ’70 Plymouth GTX (Gallery)


They say that cobbler’s kids go without shoes, and for most car builders, the saying holds just as true. Many a custom car builder has successfully produced a cavalcade of gorgeous, one-off machines for their clients only to have their own personal projects sit beneath inches of dust in the back corners of their shops. In the case of Dennis Rostenbach’s 1970 Plymouth GTX, it too was the same. Rostenbach owns and operates Roosters Rod Shop in Gaffney, South Carolina, which almost deals exclusively in classic Mopar muscle, but has been known to handle the “other guys'” cars as well.

It took nearly 20 years for work to really pick up on Rostenbach’s Plymouth, and only with the help of his son, Brandon who is 13, and daughter Nicole who is 7. Amid a full quotient of customers’ cars on the schedule, work began on the GTX. “The car was built 100-percent in-house from start to finish by us. We have done tons of Mopars in the past and know them inside and out for assembly but this car tested us in every way possible,” Rostenbach lamented. “The simple tasks became problematic and frustrating.”


“We built the car with the intentions of being a really cool driver that can lay down some rubber. We wanted to build the car with lots of new technology but not alter the beautiful body lines of the B-body Mopar… just enhance it a little,” he continued. The GTX was stripped down and hoisted onto a rotisserie, where the metal work began. Although the driprails were retained (which is a common modification), the cowl louvers were filled in, and the door handles shaved and replaced with flush-mounted Trique Manufacturing door handles (who also supplied the billet A/C vents).

Beneath the body, laser-cut subframe connectors tied the front and rear subframes together. The floorboards, framerails and factory welds were cleaned and straightened as cleanly as the body. PPG mixed a custom-hued “Brown Sugar” paint that casts a metallic flake spectrum of honey bronze to deep root beer brown when hit by the right light. Brilliantly polished US Mag 18-inch wheels wrapped in Nitto rubber fill the wheelwells, the rears which have been expanded to allow the new rolling girth.


Because Brandon wanted the GTX to be able to handily tackle any corner it encountered, the Rostenbach’s opted for Reilly Motorsports Alterkation coil-over front suspension and Street Lynx 4-link rear suspension. The big Plymouth is brought to a halt by a quartet of big, multi-piston caliper Wilwood disc brakes with Hydro-Boost power assistance. Finally, a powder coated Ford 9-inch housing was fitted with stout 4:56 gears. Because the gearing was set so low, the Rostenbach’s reached out to American Powertrain for one of their Magnum 6-speed Pro-Fit kits with two overdrive gears.

But it’s beneath the hood that really counts, as they say, and this GTX delivers. Although the firewall and inner fenders were cleaned up, much of the factory lines were retained. “Brandon was the one that decided that since this was our car and Gene Fulton was our friend that we needed one of his powerhouse engines,” Rostenbach explained. “So we gave him a 440 block and gave him simple rules: pump gas, reliable and street drivable. Other than that, do your thing.”


What they got back was a Fulton Competition 540ci stroker big block. “Gene built the engine with a carburetor,” Rostenbach laughs, “but since we are EFI guys, we modified the intake for EFI and installed the FAST system.” The EFI system was a FAST Sportsman EFI and throttle body sitting on a milled and modded Edelbrock Super Victor single plane. Even with the low profile clear-plexiglass air cleaner, the entire system fits under a flat factory hood.

But everything didn’t go as planned. “During the first start up,” Rostenbach retells, “the exhaust was hot enough to melt and ignite the MSD plastic wire separators, which then started burning along with some plug wires. So that was a minor set back. That was also the day it received it’s name from my 7-year-old daughter. We were eating dinner and I was complaining how this car has become a major problem and [was] getting to me, and she commented that it was like a ‘problem child.’ It was like a light turning on and the name fit perfect.”

To guard against any further heat issues, the TTI headers and exhaust with cut outs were covered in heat wrap and shielded with heat-resistant panels along the firewall and floorboards. Rostenbach fabricated a heat shroud over the radiator and twin electric fans, while air ducts running up from the front cowl into the engine compartment employ small electric fans of their own to pull air up and out into the engine compartment, keeping the engine always at an optimal operating temperature.

Inside the cabin is where Rostenbach’s son played his biggest role. “Brandon designed and did large parts of the custom interior and molded [the] headliner, as well as [provided] some of the sewing,” he boasted. A pair of 2014 Dodge Dart front seats were modified and rewrapped in leather to match the custom door panels and rear bench.


A unique signature of Roosters’ cars is the conspicuous replacement of the factory dash for that of a ’59 Chevrolet Impala. New Dakota Digital gauges fill the pods with Vintage Air dials front and center above a custom center console with a flat screen controlling the Alpine stereo and Arc Audio amp and Focal subs and speakers.

Upon its completion, the newly minted “Problem Child” was loaded up on a trailer and hauled to Cookeville, Tennessee, to join up with the American Powertrain crew to be put on display in their booth at the Detroit Autorama. There is made a huge splash although Rostenbach refused to enter it into the class judging, just happy to have it on display for so many to enjoy. That’s when Mopar Connection got the call that the car would be back at American Powertrain’s shop for a few days if we wanted to come and take a look at it. As you can see, we did more than that and hope you enjoy this machine as much as we enjoyed snapping this pictures.

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Kevin Shaw

Editor-in-Chief – Kevin Shaw is a decade-long powersports and automotive journalist whose love for things that go too fast has led him to launching Mopar Connection Magazine. Almost always found with stained hands and dirt under his fingernails, Kevin has an eye for the technical while keeping a eye out for beautiful photography and a great story. He's also the co-author of "The Chrysler B-Body Restoration Guide."

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