how to tell a 'no suffix' pump from the 'B' variant pump.
The grey top and white bottom typically indicates the only pump now available (from vendors or dealers), with no suffix, and that will have no chance to supply fuel when it dies. This is what is typically carried by aftermarket vendors, and it sells for about $230. Note the external hose down to the eductor jet. The eductor jet can be seen from the bottom. We pulled 25" of vacuum on the fuel line from this style pump and got no fuel. The bright green high temperature viton lines are installed with Left Coast Resident's mod, the translucent white lines are stock.
For the tan colored OEM 'B' suffix pump, with all fuel lines internal, we were able to pull adequate fuel to run the car with only 4" hg vacuum - similar to an ALH.
Note the bottom rough filter screen that covers the intake.
This pump is no longer available from dealers or vendors.
If a car has no air leakage into its fuel lines, and there is nothing blocking the eductor jet then the 'B' variant pump will allow it to run after the electric pump fails. If you have an air leak or blocked eductor jet, then it will die.