I have the 2 valve version in my 05' Excursion 4x4 with 105,000 miles and no problems and frequently tow 11,000 pounds.
Specs from Wikipedia
6.8 L V10
The 6.8 L (6760 cc, 413 CID) V10 is another variation of the Modular family created for use in large trucks. Bore size is 90.2 mm (3.552 in) and stroke is 105.8 mm (4.165 in), identical to the 5.4 L V8. Both 2-valve and 3-valve versions are currently produced. The 6.8 L uses a split-pin crank with 72? firing intervals and a balance shaft to quell vibrations inherent to a 90? bank angle V10 engine. The engine's firing order is 1-6-5-10-2-7-3-8-4-9. The 2-valve version was first introduced in 1997, with a 3-valve non-VCT version to follow in 2005. The 3-valve engines were built alongside the 2-valve engines at Ford's Windsor, Ontario LVL engine line, but moved production to the larger Windsor Engine Plant in 2009.
Vehicles equipped with the 6.8 L V10 Modular engine include the following:
[edit]2-valve
1997?present Ford E-Series, 2-valve SOHC, 305 hp (227 kW) and 420 lb?ft (569 N?m) ratings for 2000 and later model years
1999?2004 Ford F-Series Super Duty, 2-valve SOHC, 310 hp (231 kW) and 425 lb?ft (576 N?m) ratings for 2000 and later model years
2000?2005 Ford Excursion, 2-valve SOHC, 310 hp (231 kW) and 425 lb?ft (576 N?m)
[37]
[edit]3-valve
2005?2010 Ford F-Series Super Duty, 3-valve SOHC, 362 hp (270 kW) and 457 lb?ft (620 N?m).
2005-2013 F450/F550 chassis cabs
2012 Ford F-650 & Ford F-750, 3-valve SOHC, 362 hp (270 kW) and 457 lb?ft (620 N?m).[38]