72,
They are an expensive pump. I have one on my 408 (which is the one I'm converting to -20 on the outlet)
I have another on my 360 that's on the stand that I'll also do. I really like the Edelbrock water pumps.
It's really not that big of a deal though, -16 on top, -20 on the bottom. I've found that's how it's done... When everything works out okay, I'll convert my other engine the same way.