Looking to replace the water pumps on my 51 Merc Flathead. There are many aftermarket pumps available, some offering different styles of bearings to replace the OEM bronze bushings and carbon seals. They are also offered with a better impeller design. I am not looking to rebuild the old ones. I have seen them available from Flathead Jacks, Dennis Carpenter, Speedway, Bob Drake, Hot Rod Supply,just to name a few. Are they all different, or are they the same just relabeled? Please let me hear of your experiences both good and bad. Thanks.