Any 8 inch finished block would work. That is 8 and a half inches square before sewn together. You would need to do a piece 2 blocks wide by 6 blocks long. This will give you 16 and a half by 48 and a half inches and you could trim down the extra 1/2 inch or just make your seam allowances bigger to take in the difference.
Also 4 inch finished blocks. In a piece 4 blocks by 12 blocks
Or 16 inch finished blocks in a piece 1 block by 3 blocks.
Hope this helps.