That's almost 230 days of effort. Was it worth it?

Wisconsin-based Ringbrothers has established itself as an expert in classic American muscle car retromods, and whenever the SEMA Show rolls around, we know it'll have something special up its sleeve. This year, that special something is an overhauled 1965 Pontiac GTO Convertible affectionately known as Billie, and the modifications go far beyond the new bodywork. The car pays tribute to a GTO the owner's mother once owned.

Arguably the most significant changes are beneath the skin. Ringbrothers built Billie around a special Fast Track Stage III chassis from Roadster Shop, featuring Fox coilovers and almighty six-piston Brembo brakes up front and in the rear. These components should be enough to ensure this Pontiac drives more like a modern car than one that dates back more than 60 years. It also includes custom 1.25-inch sway bars, C7 Corvette end links, and bespoke upper and lower front control arms.

Then there's the engine. Ringbrothers has sourced an LT4 crate engine from Wegner Motorsports rated at 650 horsepower and 650 pound-feet of torque. Original GTO Convertibles maxed out at 360 hp when new, so you can probably understand the importance of the new suspension and braking components. In addition, a new Bowler Performance 10L90E automatic transmission has been fitted, sending power through the rear wheels.

To give the car some hope of putting its power to the ground, custom 19-inch front and 20-inch HRE wheels have been fitted, wrapped in 295/35 front and 345/30 rear Michelin Pilot Sport Cup 2 tires. Even with all that rubber, we suspect this thing will leave thick, black lines of rubber wherever it gets driven.

A new body and an espresso machine shifter

The original GTO was completely stripped back as part of the rebuild, and a custom body kit was formed, so the car now sits five inches wider than it used to. Complementing the butch new look are extended rocker panels, a carbon fiber hood with an enlarged scoop, and a distinctive new front grille. Billet machined aluminum also appears on the taillight panel and parts of the hood.

Continuing the exterior modifications are redesigned carbon fiber and steel door skins, a carbon fiber front lower valance, and a carbon fiber rear diffuser, plus a unique rear bumper. Despite the significance of all these exterior modifications, Billie keeps that classic Pontiac vibe. Making it really shimmer is a custom shade of Billie Goat Blue paint from BASF Glasurit.

No project like this would be complete without an interior to match the exterior. It was expertly crafted by Upholstery Unlimited, and the entire dashboard has been pushed forward four inches and sits two inches lower. The cabin is dominated by newly wrapped leather, 3D-printed speaker grilles, and the original factory radio unit has been modified to include Bluetooth. The gear shifter is rather interesting and is actually a modified portafilter from a coffee machine. Dynamat was called in to provide the sound deadening, and a new black soft top has also been fitted.