If I could find a single-LED type mogul base lightbulb in the 20w range I'd jump on it. I don't seem to have any luck finding them though. Apparently there isn't much of a market for them (yet). If anyone spots something like this, let me know.
Try searching for E39 base instead of mogul. There are a couple out there, but very expensive still. There are also E27 and E28 to E39 adapters, and the E27/28 bulbs are easier to find and don't cost as much.