Thread on FerrariChat for F512Ms, as well as Testarossas/512TRs/Boxers. Good place to chat with other owners or get info on the boxer-powered cars.
A European site with info on Testarossas, 512TRs and F512Ms.
Link to pictures and information about the Ferrari FX, a custom Ferrari built for the Sultan of Brunei on the F512M chassis:
Link to pictures and specs on the Hamann F512M Widebody: