for every inch a shackle is longer than stock, the truck will go up 1/2". so to get 3" from a shackle, it would need to be around 11" long or twice as long as a stock one, which is not a good thing.
to the OP, what else are you doing to the front? you're going to want more than just pucks to get the suspension/brakelines/shocks/etc right.
in the rear you can go with an 3" AAL (which, due to differences between MJs and XJs that the aftermarket doesn't seem to understand, generally lift around 2" in an MJ).