As I was watching this edition of Jay Leno’s Garage, my dad walked into the room. After about 30 seconds of contemplation he asked: “Why?”

“Why not?” was the best answer I could give. Because that seems to be the whole philosophy behind this build: why not put a radial aircraft engine in a vintage pickup truck?

It’s the work of Gary Corns, owner of Colorado Auto and Parts. The truck started life as a perfectly ordinary 1939 Plymouth that had been sat in Gary’s yard for 30 years. But its destiny was forever changed when Gary acquired a classic Cessna 195 seaplane.

Not that Gary wanted to fly the ‘plane. No, he wanted its Jacobs radial engine, and he wanted to put it in the Plymouth.

The engine’s a bit of a beast, too, with seven cylinders displacing 757 cubic inches (12.4 liters) - it’s an odd number to gearheads but results in perfect balance.

A single updraught carburettor provides the fuel - whichever way up the engine is - and a V-drive system from a boat was added to drive the rear wheels via a three-speed T400 automatic gearbox.

The build took Gary, his sons, and his poker buddies a year-and-a-half of Wednesday evenings to complete. And the effort was definitely worth it as the finished article is gorgeous.

There’s a strong aviation theme to the look, the body finished in highly polished, bare metal, with the panels riveted together. But that’s just the top of a very long list of modifications.

Inside are the seats and controls from the Cessna, including two functioning steering wheels and pedal sets, plus the central throttle lever. Which would make for a fun argument, if the passengers can’t agree where they’re going.

Unfortunately, Jay can’t take it out for a drive after his tour, because by no definition is the truck road legal, being a dedicated Bonneville racer. But he does get to start it up, and discover that those 300 hp seem to be converted into 300 decibels of noise.

It’s loud is what I’m saying.