Hi,
I plan on getting a newer truck when I get back from our deployment. 08' or newer preferably. Wondering what some of the differences and flaws are of the 1500 Chevy and 1500 GMC. And wondering if anyone has any ideas to get a little extra snap and gas mileage out of them by adding some goodies. Plan on getting metallic black or charcoal grey, ext. cab with the 5.3L V8. Thanks any advice would be appreciated!

Primary difference is with trim levels and that is about all. Some claim that GMC has a better "fit and finish" but mostly it's only the type of trim that is used.
Try looking at Google images of both models.

K thanks. Do you know if there are any differences in the electronics or stereo system they put in it or the difference between the two engines?

Using full-synthetic engine oil, transmission fluid, and differential fluid should give you 8 to 10% better gas mileage and better performance:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-11.html#post2162069