The MacDougall tartan is normally worn by those with the name MacDowell, as both names stem from the same Gaelic root, reflecting different pronunciations of MacDhugaill, or "son of Dougal."

As a side, there is a "MacDowell" tartan recently registered with the STA (c.2007) that was woven by Fraser & Kirkbright for a Fergus MacDowell, who holds the copyright (according to STA info). This would seem to be a personal, rather than family tartan, and in any case would require custom weaving, so you may as well get that Carolina you want. :-)

The MacDougall tartan is readily available, though.