In the beginning there were only three kits and they were called the Cross, Parker, and Mont Blanc. About 10-years aqgo, their names were changed to Slim-Line, American, and Euro, or some variation of those names depending on who made and sells the kits.
So the answer to your question is that the Mont Blanc and the Euro are the same pen kit.
Whether the bushings are stepped or not depends on whose mandrel you are using. The Berea "B" mandrel was sized specifically for the American and Euro so they could be turned with straight bushings. Woodcraft sold the same Berea kits, but offered stepped-bushings that could be used on their smaller 7mm mandrel.