Thanks!
1) You'll probably not be able to buy a complete harness unless you bought one of the ones being sold by Guild. When I say "replace the harness" I would build one myself. Honestly, though, if you're not gigging, I wouldn't worry much. It's not super durable as-is, but if it works it works.
2/4) All the Guilds that look similar in the same line likely start out as the same guitar then they cut them differently to work with different pickups/layouts. They are quite probably made in the same factory, but they're all CNC machined so that shouldn't matter much. If a similarly shaped SFI has what you want, then I'd bet that what you want would be easy to accomplish.
When I say "the same line", I mean that the Starfire-I SC (Indonesia) is a completely different design than the Starfire-III (Korea). Unfortunately Guild has very much muddied the waters with their terrible naming conventions
3) The modern version of the Guild company isn't like the old ones. The guitars are made en masse in Korea/China/Indonesia (depending on price point) and even if they would do it, deviating from their assembly process would likely cost more than a vintage Guild. But I can almost guarantee you that they won't. Couldn't hurt to ask, though! I love being proven wrong.
Sorry if I confused the numbers.
