here's the info about it straight from the 09 order guide:

HEAVY DUTY PAYLOAD PACKAGE (627)
Usage: Increases GVWR to 8200 lbs. for improved payload and towing
Availability:
• Regular Cab Styleside 8.0' box (145" WB) SuperCab 8.0' box (163" WB), Mid-Box Prep Regular Cab 5.5' box (145" WB) or Mid-Box Prep SuperCab 5.5' box (163" WB)
• XL and XLT
• 36 gallon fuel tank (655) required with Regular and SuperCab 4x4; optional with 4x2
Requires:
• 5.4L V8 Engine
• Max Trailer Tow Package (53M)
Includes:
• High capacity 17" 7-lug steel wheels (64K)
• Heavy Duty shock absorbers, frame and 72 amp battery
• Upgraded springs, radiator, and auxiliary transmission oil cooler
• 9.75" gear set
• Standard 3.73 axle
• LT245/75R17E BSW All Terrain Tire
Optional Equipment:
• Snow Plow Prep Package (62S)