PROVIDENCE, Rhode Island, April 20 : Investment research and analysis provider Morningstar Inc. is the latest index provider to consider revising its approach to designing its market indexes in light of SpaceX's outsize pending initial public offering. Elon Musk's space transportation and exploration business is on track to issue as much as $75 billion of stock in an initial public offering that could value the company at $1.75 trillion, making it by far the largest IPO ever recorded and