The National Highway Traffic Safety Administration released on Wednesday results from a study of 23 makes and models of pickup trucks for frontal- and side-impact crashes.The Dodge Dakota and Toyota Tacoma pickups earned top crash test ratings for 2005 models. Both received five stars for all seat positions in frontal- and side-crash tests, according to a Reuters report.Two-door and four-door versions of the Ford F-150 and Dodge Ram 1500 received top scores in frontal-crash tests. The Chevrolet Silverado and the GMC Sierra scored the lowest ratings for front passenger side crash tests, the only vehicles to post three-star ratings in that category. Both received four-star ratings for front-driver tests. However, both the Silverado and the Sierra two-wheel drive models scored the best in rollover tests. Both had four stars and a 15.9 percent chance of flipping in a single-vehicle crash, NHTSA said.The Ford Ranger and its corporate twin, the Mazda B series scored the lowest ratings in rollover tests. The two-wheel drive version sposted a three-star rating. The four-wheel-drive versions earned a two-star rating and had a 30.6 percent chance of rollover, NHTSA said.