[BR3W CITY]

i havn't taken my 66 in snow (nor would i), but I can comment on bags in winter
I live in wi and drove a bagged s10 through 2 winters. Reliability in snow/ice is greatly affected by what type of setup you go with.

The bags themselves are made of the same stuff as tires, so no worries about salt or anything getting on them. Electric compressors will draw a little more current in the cold just because of the piston tolerance; may or not be a problem depending on your battery/alt combo. Bagged rides (especially without shocks/swaybar setups) are bouncy/floaty sometimes, so mixed with ice/snow it can test your nerves if you get into a hairy situation.
In terms of maintenance and reliability the biggest things are; drain your air tank(s) down at the end of fall, making sure to get out any water, then use brake line antifreeze in the system to prevent valves from freezing.
Make sure your relays, and wiring is insulated and away from salt/ice etc. If you don't there is a chance you can erode the terminals and the connection will break right off (happend 2 me twice until i switched to a weather-sealed relay).
I would also recommend putting your valves in the bed, or protected somehow, as salt getting into the valves can damage the diaphram, or stick a valve open leaving you stranded (check valves help too).