There isn't one! X2 config maker makes the text file that configures X2.503x BIOSes from the disk. For older X2 BIOSes you have to edit the BIOS directly, then reflash it. The tool you need to edit X2.4981 is XBTool, and version 1.0.23 is the latest. You can't edit X2.4983 with any tool I've found so far!
Out of interest, why are you moving away from iND-BIOS.5003? It's the only 256k BIOS that reads its config from a file on the disk, whereas with X2.4981 you have to reflash the BIOS every time you want to make a change. Also, iND-BIOS will (according to the release notes) still boot if your eeprom becomes corrupt, which might be handy if your eeprom ever becomes corrupt!