Jay Leno has said his favorite cars are "original and unrestored," but that doesn't mean he can't appreciate a modified machine. On a recent episode of "Jay Leno's Garage," the comedian tested a Datsun 240Z with a V-8 swap...and a speedster body.

Leno saw this unusual Datsun (which was originally only available as a coupe from the factory) on the street and, as he sometimes does, flagged down the owner and invited him to appear on the show. The owner, James Smith, calls his creation a "Chevatsun 580Z" because of what's under the hood.

In place of the stock inline-6, the 240Z sports a 350-cubic-inch Chevrolet V-8 that's been bored over. Smith purchased the car in 2001 as a partially completed project, with the V-8 already installed. He enlisted his brother and father to finish the car, and the experience encouraged him to start his own restoration shop.

V-8-powered Datsun 240Z on Jay Leno's Garage

V-8-powered Datsun 240Z on Jay Leno's Garage

Smith rebuilt the engine, and swapped the 3-speed automatic transmission the previous owner had installed for a 4-speed automatic.

The roof had also been cut off by the time Smith got the car, but the work wasn't done well, he said. He and his brother fixed things, also adding a rear lip spoiler and modifying the rear bumper for a cleaner look. The car does have some extra bracing (installed by the previous owner) to account for the lack of a roof, and it feels solid going down the road, Smith said. They also repainted the Z to its current, understated metallic green.

Watch the full video for more details on this build, and to see Leno take the V-8 240Z for a spin.