Re: Replacement tires for 4x4 w/17" rims
Optimally snow tires are rather more narrow than wide. Look at rally tires. So that probably won't hurt you, and may help. There are tires for winter use certified one level above M+S (the "snowflake"), but in fact they aren't available for all sizes. For example, D range BFG KO ATs come with that spec, but not the E range.
Frankly, I'm contra to the standard wisdom here about the need for Es. In the BFGs, for example, they have the same number of belts, they are just a bit thicker. And not tons more on the sidewalls. And against that you have a stiffer tire (good for some stuff, bad for others) with less tread depth and no snowflake rating. Of course if your van is pushing 12k+ you may not have a choice.
2001 Ford E250 Sportsmobile with Salem-Kroger 4x4 conversion