Plying the streets of Santiago de Cuba is the Cadillac of people carriers. I CAN THINK of just two possible explanation for this great red machine. 1. Back in 1957, a group of up-and-comers in the Cadillac division of General Motors hit upon an idea for a bold new model that would combine the refinement and style of a passenger car with the people- and cargo-hauling capability of a truck. They called it a "utility-sports vehicle." Surreptitiously, they removed a 60-S sedan body from the assembly line and, toiling at night in the basement of the Cadillac headquarters, replaced its tail fins and rear roofline with a tall, wedge-fronted box. They weren't good welders, but hey, it was a prototype. After spraying the body a bright Dakotah Red and mounting it on a pickup truck chassis, they presented their creation to Cadillac general manager James Roche. "This," they told him, "is how we can grow our brand." Alas, they had seriously misjudged ...