Both are built on the same code base, so you don't need RUN! to use them at the same time.
Firefox-3.6.10
ftp.mozilla.org/pub/firefox/releases/3.6.10/contrib/
Thunderbird-3.1.4:
ftp.mozilla.org/pub/thunderbird/releases/3.1.4/contrib/
Thunderbird-3.1.4 does not include lightning. If you need lightning, you can still download a
compatible version from:
ftp.netlabs.org/pub/mozilla/Thunderbird/lightning%20for%20TB-3.1.x/
Greggory