Y'all are forgetting that he was asking about using a Dichro head with built-in color filtration as opposed to using below-the-lens "grade x" filters. There are a number of sources out there that list recommended starting filter packs for b/w contrast grades. The beauty of having a dichro head on your enlarger is that if you need Grade 3 3/4, you can dial that in, and you're not limited to just 3, 3.5 or 4.