Is there any reason to believe that the correct chainline for that bike isn't the industry-standard 47.5-50mm, and that somehow, somewhere a mistake was made? Is the bike stock, otherwise? Are you the one that installed the last BB?

If you can find specs for that bike that say otherwise, then of course go with the published specs. But I'd be really surprised if the correct chainline for that bike isn't the standard mountain triple which is 47.5-50mm. Especially a Giant, from the early 90s.