I got Windows 7 + WoW on a 30GB SSD with 5GB free still.
Dis you disable pagefile, hibernation, system restore, search indexer? That stuff can all be disabled in most cases. That should leave you with enough space on your SSD.
The most important thing is to let Windows 7 create the partition on the SSD; if you use any cloning program you may be stuck with unaligned partition, causing lower performance and lifespan.