I'm looking for people to have a look over these spams and give me some
ideas of some possible areas for improvement (either score adjustments,
configuration tweaks, plugins that I should try, etc.).
The spams can be pulled from here: http://micah.riseup.net/spams
It appears to me you have just posted the body text for these spams. Much
of the spam catching is done off of the header information, so knowing that
would help.
Also, knowing which tests did and didn't hit on your system would give us an
idea what you might be missing.
That said, do you use the SARE rules? There are a number of rules there
that help catch 419's.
Loren