I haven't done it, but I would assume he means the 49-54 car.
Since you are using a '51 rearend, which has the better brakes, I would look for the front brakes from a 51-54 car. Get the entire setup. You'll probably have to modify the bolt pattern on the backing plate to match the '39 spindle, but I'm betting it will work. Again, I haven't done it and don't know anyone who has. Hopefully, someone will chime in who has...