I just got Grade 2 free on paperbackswap!

I thought for sure I had seen a post somewhere that explained which Book Project grade level went with each of the DITHR levels...but I can't find it.
I know Grade 2 goes with DITHR 2/3, and I know Grade 5 goes with one of them, I think it was 6/7/8, but I'm not sure.
Can anybody tell me where to find that original post OR which books are supposed to go with which DITHR level?
Thanks so much!