With the advancements in ignition systems, I wouldn't think you need to change the gap for winter on these cars. One thing I can tell you is that the wider the gap gets, the lower the rpm's will be when the power starts to drop off. Also, the wider the gap the harder it will be to jump that gap, which leads to more work on the part of the coils and the possibility of causing misfiring. A narrower gap would be easier to jump but there's the greater possibility of any debris fouling out the gap when its smaller. Another thing with the smaller gap is heat. since there will be less loss across the terminals, the terminals might end up getting hotter, which could lead to pre-ignition.
I had an aftermarket ignition kit on my old truck where they advised to increase the gap a minimum of .010" over factory and work up from there. I did until I started to notice the power band shifting downward and worked back down from there until I found its nice spot, which turned out to be close to .015" over factory, so I have played around with this stuff a little bit.