I was moving crap around in the garage tonight (so that I have enough room to get to other crap) and, since they were in the way anyway, decided to pull out an example of each block and take pictures to document what the differences are in the bottom end structure.
Basically, the Tall deck and common block are the same on the bottom end - except that the CB has rod reliefs and the TD does not. This would only (possibly) be a problem if you were to run the thicker turbo rods in the tall deck - but why would you do that? Also, the TD has a mechanical fuel pump drive mount.
You can clearly see the increased thickness of the webbing from the early block to the tall deck, and the TD looks about the same as the CB.
First pic is early block, 2nd and 3rd are TD, 4th and 5th are CB...