I bought and used a new jesel belt drive three years ago from Jesel, I used on a 1969 440 block with no grinding needed I have bought and used gear drives, Milidon, KB and Donovans that needed the boss rounded ogg and flattened that you have highlighted in black I do have a iron wedge World block that I have not treid to use yet, maybe I have some grinding to do on it when it comes time to assemble and use it