OOPS. I see now that what I bought for my 4A was an upgraded "5 Vane" water pump from BPN, but they don't appear to be offering that anymore. I may call and find out why. Moss has a 6 Vane. I recall the add on mine saying something about the larger nyloc nut on the end shaft as well. Maybe it's discontinued or their supplier isn't reliable anymore.
I'm OK with it, but my hope that it would make a difference is gone.
Sure was fun putting it in, though. Anything to warrant living in the garage amidst my tools.