If Bell Helicopter ever gets to build new presidential helicopters for the U.S. Marine Corps, production probably will take place in Fort Worth, Texas. Bell is shifting the planned work there from Amarillo, where it builds Marine V-22s and H-1 upgrades. That's because the Fort Worth site used to build presidential H-1s before the Marine One fleet switched to larger aircraft. It will be easier to restore the necessary safeguards there than to create a new secure facility, say people familiar with company planning. Bell is teamed with Lockheed Martin and AgustaWestland unit to provide the US101, a modified version of AgustaWestland's three-engine AW101. The first five helicopters are being built in Yeovil, England, and press reports had the full production run moving there. But later assembly is supposed to take place in Texas, on U.S. soil. Final missionization for all the aircraft is slated for Lockheed Martin System Integration's facility in Owego, N.Y.