Pretty much the only enclosed impeller pumps being made are Flowkooler. They used to just rivet a plate on the open impeller, leaves a bunch of room between the impeller and body. Mine did nothing to help cooling, would not surprise me if it made it worse. Now they have a nice CNC close fitting aluminum impeller that no doubt works better. You want more flow with less cavitation, a tight fitting closed impeller should do that.
Watch aftermarket pumps.for finned impellers that are too small for the bevel. They do not cool right. I found 2 at autozone with the same part number and the impeller fins were about 5/16 shorter on one vs the other
Finally got my Dayco HD pump from Rockauto and thrilled to see it was just as Dayco pictures! (and everyone selling it uses their stock pic)
It seems that this is the only orig-style iron pump out there with the heavy duty sealed/covered impeller.