Though food trucks may be the rage, doctors in Van Nuys lined up last week outside a mobile coach containing cadavers. The nation's first mobile cadaver lab stopped next to Valley Presbyterian Hospital to give doctors a stab at cold feet. "I think it's one of the greatest skills to learn," said Dr. Ronald Belczyk, of the hospital's Amputation Prevention Center, cutting a precise incision across a cadaver foot, still attached to a cadaver shin, in a surgical demonstration for resident surgeons. The big-rig lab has toured hospitals across the nation since April with its cargo of cadavers. Its purpose: to show off medical equipment while giving surgeons a chance to practice on real bone and tissue.