I've seen that pumpkins and potatoes together are *not* a good idea, so this probably follows for sweet potatoes as well. Seems like a logical combo with pumpkins, but there may be pest and disease issues. Don't know. If your goal is to use every square inch and get the most produce out of the garden, think *succession planting* and *interplanting* and *intensive gardening*, rather than companion planting. Search those words online. Sounds like this is what you are after.

You will get lots of info on what you want to do. Lettuces, spinach, radishes early while the pumpkins are still thinking about growing. Trellises along the north side for peas and pea pods early, with pole beans and other summer legumes planted at the base of the trellis for when the peas go by. Corn does well with pumpkins and squashes as long as it is not planted so densely that it creates a lot of shade. And maybe train some of the beans up the corn... If you have more room along the north side for more trellis, try cukes and/or a small climbing squash you can get up the trellis. If the soil is loose enough, you might want to do carrots in and among the pumpkins. Onions, leeks, garlic should do very well. Second later plantings of lettuce, spinach, peas/peapods, radish.

Check out *intensive gardening*, *succession planting* and *interplanting*.

You can plant them under your corn, just like the "Three sisters garden", but there is only one type of corn, flint I believe, that works with it. You can plant lettuces and squash.

http://www.no-dig-vegetablegarden.com/companion-planting.html

There are websites all over the place for companion planting.

Good luck!