Larry Hagman is reportedly preparing to saddle up for another ride into the oil fields of prime time, starring in a series of movies for NBC in advance of an eventual one-hour series.Sources say the deal, still being hammered out, would be similar to that structured for Bill Cosby, who will star in a quartet of light mystery movies during the 1993-94 season in advance of a one-hour series the following year. The Hagman show would cast the former “Dallas” star as a millionaire who loses his fortune but continues to travel around, faking his way through a lavish lifestyle. The project is being developed by TriStar TV, with Hagman to act as one of the exec producers along with Gray Frederickson and Al Ruddy. Both the network and TriStar declined comment. Hagman starred for 14 years on CBS in “Dallas,” from 1978-91, serving as exec producer on that series as well during its final seasons. His last affiliation of any length with NBC was on the comedy series “I Dream of Jeannie,” which ran on the NBC from 1965-70. He subsequently starred in two short-lived ’70s comedies, “The Good Life,” on NBC, and ABC’s “Here We Go Again.” “Dallas” was the top-rated prime time series during the 1980-81, ’81-82 and ‘ 83-84 seasons, peaking with the “Who Shot J.R.?” cliffhanger, which remains the second-highest-rated prime time program since 1960, behind only the final episode of “MASH.” Projects like the Hagman and Cosby movies as well as a planned “mystery movie”– featuring Kenny Rogers telefilms and a revival of “Hart to Hart”– reflect NBC’s push back toward broad-appeal programming after narrowing its focus last season to the key sales demographic of adults age 18-49.