on the very rare occassion I get hold of them, I feed them raw.
Lungs are classed as offal which includes the liver and kidneys. Ive heard that offal should make about 10% of the raw diet. I just feed offal for one meal once a week. Not sure of the nutritional value of lungs but will try to find out. I suppose one of the benefits is that you would be feeding more of a variety which is what the raw diet is about.
Heart is not classed a offal as it is a muscle but should not be fed in large quantities. I feed a heart once a week.