Well - not using archive so unsure about it's permissions but every VB folder is set to 555 here except:
clientscript/vbulletin_css
That's set to 755. In this folder all files are set to 644, the rest of all VB files to 444
It may differ if you let users upload signature images and these are stored in the filesystem - then this folder requires write permission too.
And - some modifications may require write access somewhere