I am hoping I can get some feedback, I want to improve the suspension performance on my truck. it is all stock. 140,000 miles.

I drive in the city and highway 95% of the time. 5% of the time I am on ranch roads, and that is the reason for the possible performance enhancement.

I am not after the "look" of a lifted truck, I do not want aggressive tires, I will not be rock crawling or mudding. I may occasionally have 600-700 pounds in the back of the truck.

I would not mind a slight (2.5") lift, but no one seems to sell that. To me, a levelling kit does not seem to offer much in performance gains.

Your input is appreciated.

 

I'd suggest replacing the high wear components in your front end which include the tie rod ends, ball joints and idler arm. I'd replace the OEM shocks with some high quality components such as Bilstiens, Rancho's, etc.
As for the stance, I'd just crank up the torsion bars slightly to get the truck closer to sitting level and install some quality all terrian tires around a 285/75-16 or 285/70-17 size.