You will have to extend your bump stops more with a longer shock because it has a longer compressed length than a 3 inch lift shock. That is if they really are 4 inch lift shocks. Different manufacturers have different ideas on what is 3 or 4 inches above standard.
If you limit the length of your travel in some way then you are not getting the full length of travel (maybe) but maybe a bit more than a 3 inch lift shock, so over all you could end up with less travel than getting 3 inch lifted shocks to start with. But you may get more travel. This is of course depending on whether you really have 3 inch lift coils. If it is Kings then I would suggest it is about a 2.5 inch lift.
Another way is to modify your shock mounts.
Thanks Insane I have just had your coils gold embedded for more flex.
We have no probs with either Dobinsons or Procomps, some other major brands can't say this with a straight face. Like Insane said, Procomps have a better warranty and a few different options with sizes but Dobinsons are right for the 3 or 4-5 inch lift and I and my supplier will warranty them longer than the manufacturer will.
As Beastmavster said it is quite common to put a 3 inch lift shock in the front of a 2 inch lift. There is a fair bit of difference between the 3 and the 4 inch front shock though.
Shane
EDIT: I have longer shocks in my Rangie and I have retained my coils top and bottom so they stretch for more flex. I never did this with my GQ's though so I can't really comment.
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