Demon408 - Thanks. One day I'd like to reduce the text and add more pictures but I never get around to it.
There are some clever solutions to shutting down electric pumps during accident situations for those who go that route. But my preference was mechanical as I wrote there.
I should have mentioned Ryan Brown was very reasonable. A bit of a delay in shipping across the border - even back then.
tubtar - There's no passages inside. Volume capacity is determined by the little flapper valves. If a npt to hose nip is being used, it may be worth using one that has a smooth transition and ease the sharp edges on the ID. A lot of times I've seen the worst transitions on dual feed hard tube to the carb. The inside where it splits from single 3/8 tubing can often be improved.
It would be great if someone like RobMc packaged a higher capacity pump (more valves) in a smaller body so it would work with the 70 up water pumps. Maybe 4 or 5 valves instead of 6. It would still be better than the typical 2 or 3. The other solution would be a pre-70 water pump in aluminum. Then we all could use the 6 valve fuel pumps with no issue (other than a bunch of us would be moving our radiator outlets to the other side.) :)