If you are talking a Superkart chassis we need to know what make and model?
If a sprint chassis I would suggest that the Shark Shifter Honda CR250 Mount should fit the bill for the Kwak. There are options to choose for chassis tube dimensions and rear case width. You may end up having to make some small mods/spacers but I think it will be the nearest you can get. Here’s a link: http://sharkshifter.com/zc/index.php?main_page=product_info&cPath=70&products_id=1187