Check out
http://coloradok5.com/forums/showthread.php?t=170627
Your question has been asked a million times and there is no single answer. It depends on wheel backspacing, tire brand, spring rate and age/condition of the springs, phase of the moon, settling of your body mounts, tea price in China, and various other more obscure factors.
In short, 4" will prolly work for 35"s, especially if you get stiff springs.
You might need to do something about either or both driveshafts and pinion angles, depending on how you do the lift.
If it were me I'd do a shackle flip in back (prolly won't have to do anything to the shaft or diff) from, say, ORD or DIY4X
http://www.offroaddesign.com/catalog/shacklekit.htm
http://www.diy4x.com/suspension.htm (scroll down to Shackle Flip 'N' Switch)
and then up front a set of 4" lift springs, which should also not require shaft or angle changes. Oh, and heavy duty shackles for the back end of those front springs, from either of the above vendors (or others.)
I also really like the greasable poly bushings.
I see that ORD says that due to the longer wheelbase, your Burb might need some tweaking to the *driveshaft* angle, but they have a link to more detail about how to check it out in your particular case.
-- A
