Blocks won't help you in the rear. The axle is underslung. You have to convert it to overslung by adding new spring perches ontop of the axle. It gives you about 4-1/2" in the rear. I also have 2-1/2" spacers in the front with 300# springs. Also did a full subframe/ diff drop and lowered the engine and trans 2" to keep good driveshaft angles. I also run 25" and they rub a bit. Need to do a bit of trimming. You would have to have a lot more lift to fit 27".