I think I found the answer myself. Quote from the 2012 F150 Source Book: "(1) 8200-lb. GVWR is included with the optional Heavy-Duty Payload Package and requires either the 5.0L 4V V8 or 3.5L 4V V6 engine. In addition to the equipment listed above, this package also includes Super Engine Cooling, 9-channel oil-to-air auxiliary transmission oil cooler,
frame upgrade (.150 rail thickness)."

Exactly why Ford does not include this (I think important) frame upgrade in the list of included feature for the HD payload package in the order guide is beyond me.


At the bottom of page 86:
https://www.fleet.ford.com/truckBBAS...12_F150_SB.pdf