Rock,
I chose the 5" Donahoe blocks. I'm glad I did. The rear end is only slightly higher than the front - which is perfect. It looks great.
Keep in mind that I have the following up front: X-code front springs (+~1.5") and the Donahoe 3" hangar kit (~3"). That's about 4.5" of lift up front. The 5" Donahoe rear blocks are well suited for what I have up front.
Oh also - the Donahoe "Signature Series" shocks are fantastic. They are valved specifically for the F250 4x4, and provide a much better ride than the stock "Rancho" pieces of garbage.
CMOS