A buddy at work has an '06, I'll measure his and let you know. It wont be late next week though.

I also have a friend with a 2010, which one were you looking for?

Either way, I pretty much guarantee its too wide for the 4Runner. Your 4Runner is 66.5 inches wide while the Sequoia is 78.9 inches wide. They use the same rear axle/diff as non-trd Tacomas, tundras, and T100s. So, your better off finding one from a Tacoma if your specifically looking for this style diff. Unless your talking about the 2010 in that case I think it uses the Same as the newer tundra, which is a lot bigger.