stock drop of the xs are 1.5 drop so you have a 3.5 3.5 drop now.
the belltech 2 inch drop springs on the customers trucks ive done lowered the zq8 trucks .5 to .75 more. 3 inch drop springs will lower 1.5 to 1.75 more and you will need 225 50 16 tires which will lower it even more. the air dam will not be able to fit a soda can laying flat under it.
as for the rear if you go with 3 inch blocks you will need to cut the bracket off
heres on how to do thathttp://www.s10forum.com/forum/showthread.php?s=&threadid=690
i would just go wtih 2 inch drop springs and 3 inch blocks