The MotorCraft oil is getting hard to find. It is mainly only available at the Ford Dealer where I live. It is a quality oil and so is Delo. In fact any CI/SL or CI+ oil works great in the Ford PSD. I have personally used Delo 400, Delvac 1300S, Schaeffers 7000, Amsoil 15W40 and Amsoil 5W30 HDD. Now I am using Royal Purple in my 95 and Delvac 1300 in my 01. I think the most importand thing with a 7.3 Power Stroke is to change the oil at 3K if you are pulling, and 5K for normal service. Synthetic oil with a bypass, you can safely extend that.
JMO