On March 9, 1996, approximately 2355 central standard time, a Beech V35A, N8323N, was substantially damaged during a forced landing near Clinton, Louisiana. The commercial pilot and the passenger sustained serious injuries. The airplane was registered to and operated by a private owner. The Title 14 CFR Part 91 personal flight originated at 2210 in Jackson, Tennessee, and the intended destination was Baton Rouge, Louisiana. Dark night visual meteorological conditions prevailed and an instrument flight plan was filed. According to the pilot, the airplane was descending through 6,500 feet MSL, and the fuel selector was on the right tank, which was "indicating 1/4 tank," when the engine lost power. He switched to the left tank, which was "showing 1/3 tank," and attempted to restart the engine "several" times without success. A forced landing ensued to a "timbered field" and the airplane touched down with a "heavy vertical impact." Examination of the airplane by the FAA inspector revealed that the fuel tank selector was in the right tank position. During recovery of the airplane, when the wings were removed from the airplane, the right wing tank was found to be "dry of fuel" and approximately 9 gallons of fuel was drained from the left wing tank. On March 21, 1996, an engine tear down inspection was performed (report enclosed). All 12 of the Champion RHB32E spark plugs were found to have "excessive plug gap," and a test on 2 of the plugs performed with a spark plug testing machine revealed that the "plugs would not fire over 40 psi of pressure." According to the engine manufacturer, the recommended gap setting for these plugs is .016 to .018 inches and they should spark steadily when tested up to pressures of 115 to 135 psi.