On the 727 it is the same as the other engines, fuel lines run from the tanks to the engines. Crossfeeds allow any tank to supply fuel to any engine. Boeing says the engine driven low pressure pump should suction feed up to ~25,000, the electric boost pumps would be required above that point. On most 727s the apu does not require an in tank boost pump since it sits level with the center tank.
Doing a manual start just takes a taller ladder.