A Motorsport block with 55mm cam bearings has a 50mm at the last journal, a Dart block is 55mm at all 5. They make a sleeve for the cam for the last journal to make it 55mm so you can use it in a Dart block after it was made to fit a Motorsport, turn down the inside to fit and grind the OD to fit. I need to know how much press on the ID to keep it on.