In probably the last 200 or so BBC that we have built---------only one was a 427. Unless the block you got needs a crank, and/or you maybe have a 427 crank----ALLLLLLLLLL the parts out there are for 4 inch stroke (454) or longer. The on the shelf parts suppliers just don't have interest in doing the 427 parts because there is only a very limited demand for them. Go the 454 route and be comfortable with up to .125 overbore which will give you 481 cubes. The 454 does require (stock) an external balance dampner and flywheel but can be balanced internal if desired--