You know ... after thinking about it, there's a great alternative to the M20 for this application. Pick up a Saginaw 4-speed. They are a while lot cheaper, and with your wife driving it, the really deep fist gear will mean less clutch replacements. The 326 doesn't make enough power to break the Saggy, and it's relatively cheap and plentiful.
Also heed Toms suggestions about heads and cam for the future.
