A rare 1971 Chevrolet Corvette ZR2 convertible, one of only two ever made, will cross the block at Mecum's Indianapolis auction this May, and it's expected to draw a seven-figure bid.

Quietly introduced as the successor to the race-bred L88 Corvette, the RPO ZR2 Special Purpose LS6 Engine Package (to use its full name) equipped the C3 Corvette with a 454-cubic-inch big-block V-8 rated at 425 hp. That power is sent to the rear wheels through a Muncie M22 close-ratio "Rock Crusher" 4-speed manual transmission.

Other components of the package included transistorized ignition, a high capacity aluminum radiator with shroud delete, heavy duty power disc brakes, and F41 suspension with model-specific springs, shocks, and front and rear sway bars.

1971 Chevrolet Corvette ZR2 convertible (photo via Mecum Auctions)

1971 Chevrolet Corvette ZR2 convertible (photo via Mecum Auctions)

Painted Brands Hatch Green with a black leather interior, this car also has a color-matching removable hardtop in addition to the standard black convertible top.

A high purchase price meant only 12 ZR2 Corvettes were built, with two convertibles, making this one of the rarest Corvettes. This car is also the lowest-mileage ZR2 known to exist, with an odometer reading of just 8,702 miles, according to the auction listing. It's also original and unrestored, and as a result has garnered numerous awards over the years.

Because of its rarity and originality, Mecum expects this ZR2 convertible to sell for between $1 million and $1.2 million, which may not be too outrageous given the current trend in classic auto sales. Consider that a numbers-matching 1967 Corvette L88, one of 20 built that year, sold for $2.7 million at a 2021 Mecum auction. And a another L88 of the same vintage sold for $3.4 million at a Mecum auction held in 2013, in both cases smashing the pre-sale estimate. We wouldn't be surprised if this ZR2 convertible does so, too.