* * *ALWAYS USE DIFFERENT U-BOLTS!!!!* * *
Also, if you're going to buy anything for the rear I recommend buying a 2" or 3" spring lift Leaf spring and that way you can eliminate the block in the rear all together... which is better.
OR
You could get the stock 4" block from an F350, might want to check people that have lifted their 1tons since they'll probably give them away cheap. Definately do NOT stack blocks.