Rear lift and ride quality

[AHowe88]

Right now I have a 4" lift front and back, although the back is on blocks (bought it this way).

I really want to get rid of the blocks, and am trying to figure out what the best options are. The truck won't be used offroad, in fact it is barely used at all, unfortunately I live out of the country for now.

I'd like to go to a 5" or 6" lift in the rear to avoid rear end sag, which I have now.

I know I have several options.

New leaf springs for 6" of lift (http://www.sdtrucksprings.com/index....oducts_id=6350).

Or a shackle flip kit: http://diy4x.com/cart/index.php?rout...product_id=112

Will there be a noticeable difference in ride quality? On the shackle flip, if I get the 6" shackles, that would only provide 3" of lift, right?

Any input from you guys would be appreciated.