You might be able to "stretch" or "shrink" the blocks using Sharon Schamber's blocking method. She has videos on Youtube. Perhaps some combination of this with trimming will make the different sized blocks compatible with each other.
Here are links to a couple of the videos:
http://www.youtube.com/watch?v=v-3RIWhBvcA
http://www.youtube.com/watch?v=sQkF02vpVuw
http://www.youtube.com/watch?v=i6aplw_tVZc
The middle video shows her stretching a block 1/2".