I've found a nursery in Ontario, CA, which offers fruit trees (including mango!) for sale. I'm sure a phone call or personal visit will elicit all the information you're looking for re. grafts, root stock, and scions: [url=https://www.sunshinegrowersnursery.com/fruitTrees.nxg]Sunshine Growers Nursery[/url].
Note that their list says "Premium Evergreen Fruit Trees--When Available." So, even for the pros, mangoes don't seem like a slam-dunk. *sigh* And there is NOTHING as sweet as a ripe mango just off the tree. (remembering my forays in Panama filling up my bicycle basket)
Sunset Zone 17, USDA Zone 9