The 2006 Ford F-150 4.6L and 5.4L Triton V8 engines use a
front-to-back, driver's side to passenger's side firing order. Therefore, the cylinder numbering is:
1-3-5-7 (Driver's Side)
2-4-6-8 (Passenger's Side)
Keep in mind that this is looking at the engine from the front (radiator side).