I check the flow from the tank to the pump by simply disconnecting the line at the pump and lowering the line to a pan. Gravity does the trick.
Electric fuel pump pressure needs to be 3.5 to 4 psi and avoid anything higher than 5 psi. High pressure will overcome the fuel valve (needle valve) of the carburetor.
All NOS (new old stock) fuel pumps have to be rebuilt with Ethanol resistant parts in order to run Ethanol gas (E10). The original diaphragms fail quickly.
1971 Master Parts Lists (6 cyl.):
1958-62, Double action, AC 4666, GM part number 5621673
1958-62, Single action, AC 4434, GM part number 6415726
Around 1954-55, the government directed car/truck manufacturers to stop using glass (fuel pumps, fuel filters, carburetor bowls etc.) because of gas bombs during collisions.
AC Delco stopped making the mechanical pumps decades ago so what is available today may be clone parts.
If you want certainty, find a good used pump and search for a classic fuel pump restorer.
Most people go to their FLAPS and then fuss because the pump doesn't look like the old one and/or the fuel lines have to be replumbed.
One more thing, those who have tried the dual action pumps have reported that they are disappointed that it doesn't improve the vacuum wipers (still stop during acceleration and going uphill).
Wiperman.com. Just like worn piston rings losing compression, old vacuum motors leak vacuum and need a good rebuild.
If you are still not satisfied look into a vacuum assist (electric motor, reservoir and vacuum level switch) like the Electro-Vac made by Trico. Hard to find but it may give you and idea on how to make your own system.
