It seems that I'm using a quart of oil every 600 miles -- not 300-400 like I said in my first post. I checked it by:
1. Reset the trip odometer when the low oil light first comes on.
2. Add a quart of oil (I did this 1/2 quart at a time, but it doesn't really matter.)
3. The next time the low oil light comes on, read the odometer.

That's still quite a bit. After cleaning the engine a while back, I can see oil weeping out of the front top timing chain cover. I bought the camshaft seal and cover gasket, so I'm going to do that next along with replacing the ignition parts. Hopefully, it will reduce the oil use a bit.