I think the GD SF2 was significantly changed from the GD SF3 so I don't know if you'd get a GD SF2 to work. I don't know if there was a CD attachment for the GD SF3 but if there was it may have used a Sony drive instead of a Panasonic. The SF7 supports Sony and Panasonic. A CD7 will work on either an SF6 or SF7 I believe.
Maybe a GD3 might work. If all I had were a GDSF3 I might give it a try. One thing to check is the ROM size. Does the GD SF2/3 support as large a BIOS ROM as the SF7?
I'm pretty sure that if Bung were still around they could add the functionality to the BIOS of the SF3 (if the BIOS ROM is big enough).