I can only echo Malcolm Douglas when I say that this is not the "proper" thing. I seem to remember that Child did this as a hack work as part of a series on English poetry. This was an eight volume work, the other is ten volumes.

The best complete edition of Child is probably the Dover Edition. For many years this was expensive second-hand. It has sinced dropped in price like a stone (new edition?). And can be pickd up for around 80 pounds/90 pounds a set.