Welcome to the Forum!! 
Wow nice lookin rides. Its pretty cool when you have twins!
For the lift. I had a Fabtech on my last truck and was extreamly happy with it. Id go with a 4 inch that way the truck isnt to tall and it still useable for towing. With the 6 it makes the truck to high and hard to use.
For performance. The allison is known to go bad if you add over 90HP over stock so that would be the first thing you'd want to do if you want it to go fast and have killer power. Does your truck have a cat or just a cat back exhaust? If it does removing that will maekt the truck sound better and have moe power.
