There wasn’t much that could be said for the Chevy Biscayne that wouldn’t also apply to a box truck. It was a cheap way to get around during its heyday from the 1950s through the mid 70s, it offered little in the way of comfort and convenience, but it had a big engine and lots of room. Built almost exclusively for rental fleets, GM did still offer the Biscayne to consumers.

If you knew the right combination of letters and numbers to rattle off to the factory, which Chevy sales manager Karl Bill did in 1966, you could order quite the muscle car right from the GM factory. This included the venerable 427 cubic-inch L72 big-block motor, nominally rated at 425 horsepower, which Bill’s ‘66 Biscayne drag car dubbed “Bonanza” packs under the hood.

This rare GM oddity is heading to auction next month at Mecum’s Indianapolis auction, and although it isn’t likely to set any records, it would make a fine show piece or an even better weekend warrior. Not only does it have the L72 (which has been dyno tested at 470 horsepower, far more than GM’s 425 rating), this Biscayne also packs a M21 Muncie four-speed manual, 4.56:1 gears in the 12-bolt rear end, the F41 heavy-duty suspension and beefed-up brakes to bring the big Chevy to a stop.

Bonanza became a regular fixture at New York drag strips for obvious reasons, and it reportedly ran as fast as 11.73 at the drag strip. After Bill was done with it, Bonanza passed through a series of owners until finding John DeRue, who mounted a rotisserie restoration that brought it back to racing condition, save for some more streetable 3.70:1 gears out back. Wearing a little over 7,200 miles and being one of just 200 Biscaynes similarly equipped, auction experts expect Bonanza to fetch as much as $100,000 at next month’s Indy auction.