DavidP2001

Thank you, I greatly appreciate your comments!

The vehicle is a 1999 GMC Sierra 1500, 4WD with the push button 4WD engagement to the left of the steering wheel. I can hold down two buttons simultaneously and put the transfer case in neutral. The owners manual says it can't be flat towed, but if this is true, I don't understand why not? I know later models with the same push button 4-wheel drive engagement can be flat-towed, but why not this one? Thank you for you comments!

Thank you Mike, I appreciate your feedback. So, since you specify that an 02 LS6 will work with existing components, I assume that a 99-02 LS6 will work?

I have a nice 99 stepside that I inherited from grandad and it has great sentimental value to me. Although it has 185,000 miles on it, and the 4.8L engine doesn't burn a drop of oil, it leaks oil rather significantly. Also, as most will know that have a truck with this engine, it is greatly underpowered. Would it make sense to replace the engine with a 5.7L LS-6 available from a friend who owns a salvage yard? Is this a difficult swap? What about the computer/ECM currently in the truck, do I replace the computer/ECM with one for an LS-6? One other data point is that the frame has fairly significant rust. Many thanks for you comments!