OK! Try this path ftp://ftp.ni.com/support/labview/updates/windows/, and go to Win3x, and then go to 31-to-311.
If that doesn't work go to http://digital.ni.com/softlib.nsf/display?ReadForm&lookup=LabVIEW&view=weballsoftware&node=132070_US, and then go to Windows 3.1, then Update, and then LabVIEW for Windows and Windows NT 3.1.1 Updater. Maybe, you will have to fill out a profile webpage, but that's easy.
Hope this helps,
Aguila