Email or call S&W. You can find in online auctions also.
If you are looking for the owners manual you can find it at the link below.
You can find a 1985 Chevy G 20 Van owners manual at most Chevrolet dealerships. Many auto-parts stores can order you an owners manual.
internet, Cooters auto manuals
If you don't have a manual, find a gunsmith and ask for help.
go to auto zone
As of Aug, 2009, you can find the manual for it here: pdf.textfiles.com/manuals/FIREARMS/jchiggins_88.pdf
Follow instructions in the owners manual. Find a gun smith if you don't have one and ask for help.
some times the auto wreckers in your area will have them
You should find this information in your owners manual. Also you can get a manual for your car at an Auto Zone.
Owners manual. Call a GM dealer. Auto parts store.
Tesco, Brighton