Just hook it up, set the limit screws, and see how it runs. Triples aren't really "indexed" in the way a rear D is, you actually do use the index positions to adjust where the FD is to prevent the chain from rubbing just like you do with friction shifters. I can't 100% promise it's going to work, but I'm betting it will shift from low to high with three or four clicks, and give you usable positions down one click from that and up one click from the low position.
Also, check out swap meets and maybe even put a WTB in your sig, sora brifters are pretty common components in people's parts bins.