Palin is a lot of things, but Margaret Thatcher isn't one of them.
Thatcher was a world-class intellectual, one of the brightest and most articulate politicians in the last 70 years. She was an accomplished academic, legislator, author (no ghost writers for Thatcher) and statesmen well before she became Prime Minister. Most importantly, Thatcher didn't ever evoke the populist rhetoric that Palin seems to embrace. Thatcher was an elite amongst elites, of that, their can be no doubt.
Aside from both presumably standing for smaller, less intrusive governments and a strong military and foreign policy, there's not much else that's similar between the two women.
Great post, bumping for future reference. You said it much better than I.