Under the car is the only removal option, as the lower fastener is inaccessible through the front access hatch. Remember that the upper nut need not be completely removed, only slacked off since most fuel pumps have the mounting boss slotted for convenience in pump changing. In case you're changing it 'cause the old pump quit, also remember that the 351-C fuel pump eccentric is bolted to the front of the cam, and the bolt sometimes loosens, allowing the eccentric's driver-tab to pop out of its cam recess. This stops all mechanical pumps from working until fixed. If this is what happened, you'll realize it when you change pumps and you feel no resistence on the spring-loaded arm going into the engine, or that things rattle a bit while inserting the new pump. The cam can be accessed with the engine in the car.
