how does that affect your rpm's (and fuel efficiency) though if you go with the 4.10 but stick with the stock tire size? doesn't it rev higher at cruising speeds or is that something that can be corrected with a custom tune?

i currently have the 3.55 LS but i may install a 6" lift with 33's so i am thinking about replacing the diff gears

 

Hey ZOMBIE-

Sure, revs higher throughout the driving range. If you do a lot of freeway driving you need to weigh the options.
With my speedo corrected for the 410's I am running 2,200 rpm @ 70 mph
- very noticably higher revs than the 355's.
I drive mostly surface streets with 31" tires, and I only wanted better acceleration and performance.
Try searching tire size and gearing - I'm sure there are more informative posts that would be helpful.

 

If you're going to do a true 6" lift, you're probably going to want to step up to some 35's and 4:10's at a minimum. If I had a 2WD, I'd have gone 4:10's long ago.