The airplane was on a U.S. Navy mission and flown by a Navy aviator; another Navy aviator occupied the right front seat. While over mountainous terrain, the engine sustained a catastrophic crankshaft failure. The pilot elected to proceed towards higher terrain, bypassing lower and more suitable emergency landing areas. Internal communications between the right seat occupant, a more experienced pilot, and the PIC indicated they planned to stall the airplane prior to landing on an upward sloping mountain ridge. The pilot misjudged the altitude and stalled the airplane. Both pilots were killed. The investigation revealed that the crankshaft failed due to inadequate torque of the through bolts causing fretting and galling on the crankcase halves. The engine had accrued 618 hours since major overhaul and had experienced 7 vacuum pump failures due to misalignment of the crankshaft drive gear. The through bolts were removed by the operator to repair the No. 3 Rosan stud 322 hours before the crankshaft failed.