Your between a rock and a hard place here, sorry
Sadly, there is no frame available for your system. And the SSD will be too fast for your system causing other problems.
I also wouldn't do it as your OS (OS-9 or early version of OS-X for PowerPC systems) does not have the needed support of SSDs TRIM services so you'll wear out the SSD out prematurely.
I would focus on upping the memory if you can and if you can update the hard drive to a larger drive (if you have limited free space) to gain what you can with this system.
Otherwise its time to safe ones pennies for a newer system (even a used Intel based model).