I find that the simple mechanic behind OD&D is easier to adapt to campaigns like Dresden than d20, because d20 makes use of so many more details (such as skills and feats). Uing the old OD&D rules, it's easy to throw together a quick spell list and get players underway. Monsters are rated by only a couple of stats, so they are easier to convert as well.
If you don't have access to OD&D, you might google search for "Swords & Wizardry" (which is an OD&D clone) or OSRIC (which is an AD&D clone) because both are simple and are free downloads.
Another adjustment I tend to make is forcing wizards to be a fighter-mage or thief-mage, in order to control their magic level somewhat.