Good info! I think I'll just dispose of the bypass idea. I have the fitting that GMC made to block off the bypass when you added a heater. I assume that this was the fix instead of just removing the bypass all together and connecting the heater hoses directly to the water pump and thermostat housing. On a cold winter day I'll want the heater to work to it's max capacity. I'll try the engine setup without the bypass and if it don't work I'll put it in. As always, thanks for the info and any more tips are appeciated.

"The Operation of GMC trucks is normally smooth and steady, with no loud rattling, knocking or unusual noises. A good driver will quickly become accustomed to driving a GMC truck and will get the feel of his vehicle regardless of his engineering knowledge."-TM10-1563