Stupid questions please don't hate on me too much

I put my 5100's at the highest setting (2.5) and had the TSB performed along with a 1" block on my 2008 DC which allowed me to be bed high by .5"

Adding 265/75/16 dropped my gas mileage 1mpg by itself.

Prior to the lift/tires I was getting 19.5 - 20.5

After lift/tires I was getting 18 - 19

...and yes I drive like a grandpa with my truck

 

Thanks for the help guys. So my plan of action is to take it to the dealer to get the rear TSB done then take it to a shop to get the 5100s installed and set at 1.75" then to a tire place for some 265/75/16. Sound like the right plan?

 

Throw an alignment in there after the 5100s.

Or I did the 5100s first and got the alignment from the tsb.