The page is available @ FDA.gov ArchiveFDA does have an archive page "FDA.gov Archive" but appears limited when I tried a search, but you could try it.
I do believe they archived anything earlier than 2005 and you'd probably need to do an FOI (Freedom of Information) request. I found an interesting WSJ article from 2015 regarding this change, sorry I can't post link but you can probably do a web search for "wsj" and what-did-the-fda-do-with-some-of-those-old-warning-letters".