Ok, I have been calling parts stores for a water pump for my 48 plymouth that now has a 51 motor in it. I am totally confused. Does anyone have pics of a internal and external bypass water pump, so I can get a hold on what the blazes is going on. I found something on this web site about the difference, but the pics did not come up. I think the backing plate is different and the top were the external bypass went is either not there or different. HELP!!!!!!