Carter Racing Mechanical Fuel Pump

The problem with the 6 valve pumps that I ran into was the housing diameter interferes with the '70 up water pump inlet.
Maybe Clay's pump housings are smaller diameter, but that's what I found on the
More valves in and out help flow without requiring more pressure, but require more room - and maybe a bigger diaphram.
A couple of pictures here.Mechanical Fuel Delivery for Mopar LA Engines