ALLEN PARK, Mich.—In this suburb just west of Detroit, Ford Motor Co. is working on one of the biggest gambles in its 108-year history: a pickup truck with a largely aluminum body.

The radical redesign will help meet tougher federal fuel-economy targets now starting to have wide-ranging effects on Detroit's auto makers. But Ford will have to overcome a host of manufacturing obstacles, plus convince die-hard pickup buyers that aluminum is as tough as steel.

Ford is hoping the switch to the lighter metal will cut the weight of its F-150 truck by about 700 pounds, according to Ford executives familiar with the company's plans. That is roughly a 15% reduction for the F-150, which is the company's most popular pickup in the U.S., favored by farmers and suburbanites alike. Such a reduction would enable Ford's trucks to go farther on a gallon of gasoline, and open the door to other changes, such as the use of smaller engines, that can further boost fuel economy. Along with the aluminum makeover, the new F-150 also is getting a more muscular look, according to one Ford designer.

In the summer of 2011, the Obama administration pushed through new fuel-economy regulations that would require the U.S. vehicle fleet to average 54.5 miles per gallon by 2025. The requirements ramp up fuel economy goals for vehicles of different sizes each year.

The new Ford truck is being designed to come out in 2014 capable of hitting the increasing fuel economy standards through 2020, one of the executives familiar with its plans said. That would equate to roughly a 25% improvement in fuel economy. One of Ford's most popular trucks, the 2012 F-150 four-wheel drive with the 3.5-liter V6 engine, now gets 17 miles per gallon combined city and highway mileage.