I think, there is like 3 different impeller designs (I'm not positive, on this) and vanes AND depth of impeller in to the front cover housing. I know this created confusion, that our old parts department had pictures on the wall, of the different water pumps, just for 3208s. 

There are differences and there were many times, the parts guys, would set old water pump (customer bought in, with him) next to "new reman pump" before customer left the building. 


Not one size fits all. (but some "bolt on", but impeller is too short, in depth = bad)