You need a Chevy or GMC VortecMax Package like this:
The Vortec High Output option was first introduced in 2004 to a limited market (mainly consisting of
Texas and several surrounding areas); it was available nationwide for MY 2005. It was available for both the Chevy and GMC 1500 series trucks. This special edition package (under option code B4V) included several options previously not found on the standard 1500 model, most notably the LQ9 6.0 L V-8 engine (the same used for the Silverado SS, the 2005-2006 GMC Denali's and the
Cadillac Escalade). The LQ9 motor was rated at 345 hp (257 kW) at 5200 rpm and 380 lb·ft (515 N·m) of torque at 4000 rpm, which was the same specifications shared in the SS models. The B4V package could only be ordered on extended cab standard box 2WD trucks. They were all built at the Canadian assembly plant and were equipped with the Z60 High Performance suspension package, in addition to the M32 = 4L65E transmission, GT4 = 3.73 rear gear, and G80 Gov Lock as standard equipment. The 2004 models were equipped with the standard 10 bolt 8.625 rear end. The 2005 models were upgraded with the larger 14 bolt 9.5 rear end under RPO option AXN. The package also included one style of the newly introduced GM 20 inch wheels installed from the factory. This marked the first time the LQ9 engine was available for a two-wheel drive application. Unlike the previous years with the SS Package, you could order the interior combination in anything from basic cloth to fully loaded. There were also more exterior color options available with this package.
In 2006 The package was renamed the Vortec Max package. The Vortec Max package was added to the option list with an array of similar features and new badges. However, the Vortec Max package differed in that it also came with a variant of the Z85 Handling/Trailering suspension, as well as 17-inch wheels and tires under the option code NHT on 4x4 models versus the Z60 High Performance Suspension and 20-inch wheel and tire package of the regular B4V 2 wheel drive Performance Edition. This was because the Vortec Max package was intended for max trailer towing, while the Performance Edition was intended more for customers who wanted the Silverado SS mechanical's without the visuals of the SS. It was also made available (in addition to the extended cab) in the light duty 4 door crew cab models. For the first time it was also available in 2 wheel drive or 4 wheel drive on both the Silverado's and Sierra's, with or without the Z71 package.
The newest Vortec Max performance package introduced in 2007 on the GMT900 includes a 10,800 pounds towing capacity. 367 HP... basically the 6.0L engine with the 6.2 heads.
I have a 2007 GMC with this package and use it exclusively for towing up to 10,000 lbs. delivering oilfield parts. 120,000 miles on it and never had a repair done other than regular maintance.
Mine is a Crew Cab with an Undercover flip tonneau cover. Best truck I have ever owned. 18 MPG empty & 10-12 loaded at 70 MPH.
Good luck,
TC
