I have a couple of images of belly mount mowers on a B on my website (links below) - that may give you an idea. Not too much to hooking it up - just time and effort.
I have a Woods L59 60 inch mower on my 1949 B and that's a real nice combo. I use it to mow the yard, but Saturday afternoon I mowed a ditch with 10-12 inch tall grass (or better) down to around 5 or 6 inches. Pulled it hard, but it handled it - just had to make two passes because I had let the grass get so tall. The temperature gauge never moved ..... and this was a ditch bank 20 feet wide by about 1/4 mile long. I do like that B!
Sandy Lake Implement offers Woods mowers (firstname.lastname@example.org or 724-376-2489) as well as Paul Bazetta (http://www.tractorbuddies.com). I think a L59 mower will cost you around $1300 to $1600 plus freight.