Depending on the brand/manufacturer, the belly mowers attach to a right angle drive mechanism (usually referred to as a mule drive) or to the the tractor final drives. Connection links are usually angle iron from the mule drive to the mower deck and a lift link connects the deck to the hydraulic lift or manual lift. Each brand has slightly different connecting points. BTW, suggest you start a new post on either the Farmall Cub page or the Numbered LoBoy page. You'll get a lot more viewers and responses to your questions. :hattip:
EDIT: Now that you have 3 posts, you can access the manuals info at the Quick Links tab, top left corner of this page. There is a lot of information there showing how mowers and other equipment attaches to the tractors.