It is worth noting that the feedhorn on the Prodelins (at least the one in the picture, which is identical to my 1.2M Prodelin) is NOT the common C-120 flange. It is the same size, but the bolt hole configuration is slightly different. You can mount a C-120-flanged LNB such as the FSS LNB from a Superdish on it, but you'll either have to drill new holes or use fewer screws to attach the LNB to the feedhorn. I just went out and looked at mine, and it seems only two of the four screw holes on a C-120 LNB will line up.
Mine was in use at a friend's house with only two screws in place for years, and there was never any trouble. Be sure that the O-ring is in place between the feedhorn and the LNB, and you'll be weathertight. Using that feedhorn will be important if you ever do find the same dish without one (or with a damaged one).