LAS VEGAS — Imagine if you were Tim Sinor, the affable Oklahoman in charge of Freightliner Specialty Vehicles. At the height of our country’s Supersize craze, his company’s semi-based pickup trucks were considered the ultimate in cool.

A testament to the measured lunacy of SEMA, the annual showcase of aftermarket auto suppliers, Mr. Sinor’s ominous Sport Chassis P4XL doesn’t look out of place at here the show. But beyond the confines of the convention center’s display area, the four-wheel-drive P4XL may be the most irrelevant vehicle in the United States. XXL has gone out of style, and the P4XL could be the movement’s poster child.

This is not to say that the truck hasn’t employed elements of style. Mr. Sinor’s team procured the materials for this display model’s enormous leather-lined interior from the same suppliers Mercedes-Benz uses for its AMGs. Obviously, many more cows were needed for the P4XL; leather is slathered throughout the covered rear cargo area. The buttery hides are sumptuous, and the installation is meticulous.

Fitted with a Cummins diesel that churns out 1,000 pound-feet of torque to four giant Michelin radials, the P4XL appears ready to yank a row of townhouses from their foundations. While most Sport Chassis models use the acclaimed 6-speed Allison transmission, the all-wheel-drive P4XL uses a 5-speed with a shift-on-the-fly transfer case. The truck is certainly capable, and likely more so than most would be buyers would ever require.

Sport Chassis does know how to outfit a truck, but with a range of prices from $150,000-$250,000, the credit crunch has hit his business hard, Mr. Sinor said. “We built the first Sport Chassis medium duty truck back in 1996. They were originally designed for the well-heeled horsemen. Slowly, things expanded, and then just a few years ago they really expanded when other segments of the population saw that our truck existed. Then guys with motorcycles, sand rails, boats, planes and fifth-wheel travel trailers all wanted something different than a regular pickup to haul their toys with.”

Mr. Sinor turned to his P4XL and said: “We still offer something different, but many of buyers need credit, and that has just dried up. Things are slow.”

Mr. Sinor told us that his group will make it through this downturn and he fully expects a segment of the population to return to its Supersize ways. When it does, his company will build their trucks.

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Slide Show: Highlights from SEMA 2008