We have a similar solution for 456s and 550s using a Camry space-saver spare:...
We have a similar solution for 456s and 550s using a Camry space-saver spare: http://www.ferrarichat.com/forum/456-550-575-sponsored-bradan/372763-456-spare-tire-kit-about-%24100-4.html
Slightly off topic, but I eliminated the need for an Allen wrench for the removal of the laterals using the knurled nuts from Oz/Gothspeed. Super easy access now.... http://www.ferrarichat.com/forum/348-355-sponsored-bradan/253657-tool-free-access-355-engine-compartment-battery-terminal-posts-possible.html