The blocks will raise it 2" and are 1-3/4" wide to match the leafs. They might be longer than they need to be, but I don't know that it matters. They will not be bolted directly to the leaf springs.
In hind sight, it probably wouldn't have cost much (if any) more to just measure the free dimensions of the springs and get some with higher arch. At this point its a matter of pride and making this work safely.