245 horsepower. That's the output rating of the naturally aspirated 5.7-liter L98 V8 found under the hood of a C4 Chevrolet Corvette, at least until 1992. While many modern economy cars boast that much power, at the time, the C4 was considered one of the coolest and best sports cars in America. Aftermarket companies were also well aware GM's V8 was capable of much more.

Enter Callaway Cars.

The renowned Corvette tuner from Connecticut struck a deal with GM in 1987 that enabled it to modify and partially build their idea of what the car ought to be. In fact, it was Chevy who approached Callaway after seeing the latter's modification work on twin-turbo Alfa Romeo V6 engines. The result was the B2K Callaway Twin-Turbo. It was even available for purchase at Chevy dealerships. All customers had to do was check the box for the "RPO B2K" option on the order sheet. GM and Callaway took it from there.

That process involved the C4, built at the Bowling Green, Kentucky factory, being shipped to Callaway. Because of this arrangement, owners benefited from the same factory warranty plus an additional one-year, 12,000-mile warranty courtesy of Callaway. This conversion, not surprisingly, didn't exactly come cheap. A C4 coupe cost at least $32,000 at the time, while the convertible was priced from $37,000. Callaway requested an additional $27,000 on top of that and it was definitely worth it.

The C4's engine was removed and underwent numerous modifications, including the addition of a pair of turbochargers. The new output was rated at a conservative 382 hp and 562 lb-ft. Owners didn't have to worry about additional registration requirements because the car was still classified as a regular Corvette by the EPA.

Around 500 C4s were ultimately converted through 1991. While most examples likely still exist, they don't come up for sale often. Fortunately, today is one of those days.

This 1989 Chevrolet Corvette Convertible Callaway Twin Turbo is up for sale on Bring A Trailer with just 6,000 miles on its odometer. What's interesting about it is that aside from being #02 of 68 examples built by Callaway in 1989, just 25 were convertibles. Finished in Medium Blue Metallic with a white soft top with an interior boasting the same colors, a Callaway AeroBody kit was added in 2007.

This example has a heavy-duty four-speed automatic gearbox sending power to the rear wheels. Other features include heavy-duty brakes, a power steering cooler, sport mufflers, magnesium wheels, electric climate control, and power-adjustable sport seats. A special Callaway badge can be found on the interior's center stack.

Its original owner kept it until 2004 and its second owner had it for just three years. Its current owner/seller has added just 150 miles. The auction won't end until this coming Monday but already the bidding has passed the $40,000 mark. We fully expect it to surpass the base price of a 2021 Chevy Corvette by the time all is said and done.