Brown & Sharp 1-2-3 blocks have the tapped hole in them I have two setsTry to find a set that the bolts will fit through the unthreaded holes. There are a lot of sets out there on ebay and through some importers that the bolts don't fit. I have a set that I got from enco and not being able to use the included bolts they have very limited uses.
If you can talk with the seller to make sure that they do otherwise you are wasting your money.
I just bought the cheap sets and re drilled the holes with good bits...
I have this set from LMS $29.95 .0001 in all measurements and ground hardened:
http://www.littlemachineshop.com/products/product_view.php?ProductID=2881&category=