Optiplex 780 DT, SSD options

Greetings,

I am interested in replacing the old 3.5" hard drives in some old optiplex 780 desktops with new 2.5" SSD hard drives. 

I'm wondering if anyone would be able to provide some helpful insight into the following:

The manual for the optiplex 780 indicates that the maximum size for a 2.5" SSD in the optiplex 780 can be 64 GB. So, I'm wondering what would happen if I installed a 120GB SSD, would it not be able to utilize all the disk space, has there been firmware upgrades since the original manual that would allow it to read larger SSD's now?

Thank you.