The base SR system works fine for other settings. If you're porting your character back in time there really isn't much of an issue. If you want the competition to be able to compete with the heroes, you may have to make a higher percentage of the population awakened (Adepts and Mages) or have enchanted items exist for mundane characters.
If you're wanting to actually start up a D&D game using the SR rules, it's pretty simple to do. The only real factor that can ever crop up is balancing awakened vs. mundane since there is no cyber. This can easily be done by introducing enchanted items to replace cyber. Essentially, enchanted items interfere with an awakened's magic (just like cyber causes magic loss). You can then just port over most of the cyberware as enchanted items (internal air tank is a Ring of Breath for example) and use the same rules for everything. You pop in Bioware as high grade enchanted items and everything is gravy.
My group has used the SR4 rules for just about everything from Weird Wars to Star Wars to Indiana Jones, and they work great as long as you cut the parts that don't fit the setting you're playing in (Obviously there is no need for magic or cyber in Indiana Jones really for instance).
