I have two 13w3 cables that I'm not using. alternately, Sparcs look for a terminal connection on the serial port if there is no keyboard/monitor connected to the machine. You can also use a vga adapter, you'll need to reset the NVRAM parameters on the Sparc by typing blind, but it can be done.
That external CDROM is a nice find, hang on to that one. I had a lot of trouble finding a cdrom drive that was sun compatible.
I've had a lot of fun restoring old Sun's, enjoy!