Pontiac engineering for 60s preproduction.
 

So this stacked 4 gear pump is one ways the factory was looking into more pressure and volume for SOHC 3 valve per cylinder motor.

I guess that was cheaper than making a deeper casting with longer gears?

Actually, staring at the photo for a while, the pumps have a common inlet (the screen), but separate outlets. That way, the output of the lower pump could be dedicated to top-end lubrication. And each pump could have its own pressure regulator, which you couldn't do with a deeper single pump. Clever!

Thanks Steve. I may have seen that before.