I was ready to adapt a vertuical head to a hiriziontal BM that I have, when I came across a genuine BM head for the huge price of $5 five bucks, at a tool sale. I picked that sucker up right away, of course. Needed new grease seals, but it works fine.
The BM is not much of a horizontal mill, but the vertical is stout enough to do most any work that fits on the table. Yeah, it is a small machine, but if you have small work, it can be handy. The only big issue is having no quill. Aside from that the head is a bit big compared to the table, hard to see under, But useful enough that I'm not kicking mine to the curb just yet.