The switch with a side post is for 12V systems. It supplies full 12V to the coil when the starter is engaged.
Many people ground the battery to a starter bolt. How many grounds varies. Your frame should be grounded and the cab should be grounded to the frame. The bed was grounded to the frame by the mounting bolts when it left the factory. These tend to corrode after 50 or so years so I like to run a strap from the bed to the frame, too. Tail lights tend to work better that way.
