For invisible files, I always used DiskTop. I'm not sure how it was initially sold, but it was bundled with copies of Mac Secrets, 2nd Edition. (The book is a must-have for any Mac enthusiast and the software collection accompanying it is also quite good; DiskTop is just the tip of the iceberg in terms of selection on those three floppies).

DiskTop is a DA and a worthy Finder replacement. Since you're using System 6, it is especially handy for those times when you need to manage files without MultiFinder turned on. Invisible files are displayable.