I'd recommend against a 6" lift on a Blazer. Will likely need new driveshafts and brake lines, and that much lift makes the vehicle taller than necessary (i.e. easier to roll). You can fit 35s with less height. With that being said, I wouldn't recommend 35s on stock 1/2 ton axles, because of gearing and lack of axle strength. If swapping to heavier duty axles, go for it.
