Just barely.
A current Win 7 or 8.1 install will be around 40-45GB, once all the updates are done.
An SSD needs about 15% free space. So that leaves ~55GB actual usable space on the SSD.
You're going to have to be very, very careful about space management.
What are your prices for 64GB SSD vs 120GB SSD?
Several manufacturers no longer make and sell a 64GB, because they're too small.