tried to measure from the ground up to the bottom of the upper wheel arch? like right in the center of each wheel, up to the bottom of the fender lip?
That could tell you about how much difference there is. I cranked mine up and it's not level looking, but my front and rear is at 37 inches with some small 255/70-16 tires.
So with this info let's say you got 40 inches in the front, and 37 in the back, you'd want a 3 inch block or bigger to level it out, bigger if you want rake. if you got 40 out front and 38 in back a 3 inch block would be perfect to give you about a 1 inch rake. it depends on how much rake you want really. I think factory the back is 2 inches higher then the front, so if you went up 2 in the front from stock you'd want 2 inches in the back to keep a rake, a 3 inch might be too much, and 1 inch or 1.5 might give it slight rake but almost level or level.
So I'd find a level spot and measure it up and get an idea or where you're at first.