To begin with, I've arranged to have your post moved from the Solaris 11 forum to the Solaris 9 forum.
That's the closest arena for questions involving a system running Solaris 8, as you stated in the title of your post.
I think you have a Filezilla issue, not an OS issue.
It's been a very long time since I needed to investigate deep into Filezilla's settings but I recall there's some various choices as to 8-dot-3 versus long-file-name compatibilities.
My various systems with Filezilla installed don't have your issue and they're all installed with what I vaguely remember as its program defaults. When I use the program it is ALWAYS to transfer files back and forth between MSWin and *NIX systems.
You might think about searching for hints and solutions on Filezilla forums/blogs/wikis instead these forums here.