Idaho-based customizer Rtech Fabrications has been busy building retro-themed dream machines like the Ponderosa and other fabulously large pickups that can block out the sun when parked. 

Owner Randall Robertson stopped by Jay Leno's Garage to talk about his creations and the fabrication processes for his massive—and massively cool—restomod pickups.

Jay Leno takes a prototype Ponderosa for a spin. It's a 1966 Chevrolet K30 grafted onto a duallie flat-bed chassis with a massive 175-inch wheelbase. It's powered by a rather Ram-like 5.9-liter inline-6 Cummins turbodiesel mated to a 5-speed manual transmission. Robertson admits that a Cummins-powered Chevy may sound like heresy to diehard Bowtie aficionados, but he says it's the best mate for the truck that weighs more than four tons.

The list of upgrades and fabrication needed to make Robertson's amazing creations is long and extensive, but our favorite parts include the ported and polished motor, 60-gallon fuel tank, fabricated all-steel crew cab, and Bluetooth-enabled retro radio. A 5-speed manual sounds delightful, but we'd prefer to live in Rtech's hometown of Couer d'Alene if we had to drive it every day—traffic would be miserable in a big truck like this.

Robertson also brings along a 1972 Chevy that hasn't had quite as many upgrades, though that's coming. It began as a 1969 or '70 mode, but it has '72 door panels to make it a '72. It has the same Cummins engine, but it is soon to get a 1,000-hp twin-turbo Cummins engine, as well as new suspension and new steering.

Leno drives the enormous 1966 Chevy Southern California and it dwarfs everything else on the road.

Check out the video above to hear the big rig slog around town and see Rtech's huge pickup rolling on the road. It looks like nothing else.