They make better modern versions of that ditch plow, but why not just use a bulldozer with a 6 way blade? I am including a YouTube Video of it, but honestly a bulldozer with a 6 way blade can accomplish the same thing, with a few more passes granted, but still a nice finish on the swale. Last year I installed a half mile of swale and then got hungry and then stopped for lunch!
To do all that it took about 4 gallons in diesel fuel, 4 hours time...and the end result was a perfectly shaped swale.
I have my own bulldozer granted, but a small 450 John Deere only costs $350 a day to rent, and $85 in delivery fees.
(BTW: Walt Chase is right on target as well, I am just adding another piece of equipment that excels at the job as well and can be rented for reasonable cost).