Note 3-11-2011: I am having trouble finding the inertia switch (615Z-9341-A and the 3 wire connector 96-7552) as soon as i find the number i will add the new number to this item
                            I have new numbers for the inertia switch. From any Ford dealer parts dept. order switch number (5L2Z-9341-A or 5L1Z-9341-A) and wiring pigtail kit WPT-1001, 3U2Z-14S411-NUB. This number is also good from Ford (6L5Z-9341-A and the 3 wire connector 96-7552) as you can see the number above is wrong, the (L) was a (1). Local Auto Parts dealers should be able to order the parts from Ford. The cost should be about $30 to $40 dollars for the switch and pigtail kit. Then follow the mounting instructions and wiring in this article.

Adding an Electric fuel pump is a safety concern for older cars and trucks. If you want to add the fuel pump then a roll-over inertia switch should be added.
One like used in the late model Ford products can be used. It is easy to install and will stop the fuel pump in the event of an accident.  I would consider such a switch a "MUST" when installing an electric fuel pump. The Ford switch has a manual reset, so they can be reset if activated by a bump or some other minor disturbance. When installing the switch make sure the switch is level and mounted in a vertical position. The car / truck should be level also to have correct operation.  Mount the switch so you would have easy access if it is tripped. Most Ford products so equipped have the access port in the trunk or passenger side panel just in front of the door interior where the switch control may be accessed if a reset is required. The switch has a normally open (NO) side so that wire can be used to turn on a light on the dash so the driver will know if the switch is tripped and needs to be reset.
For a switch the abreavations are C = common contact and NO = normally open side contact and NC = normally closed side contact for the switch.

Make sure to mount the inertia switch in a vertical position on a solid part of the body of the car or truck.
Put it in a place where it will be protected from water and other road material.
The picture below is a wiring diagram for the Ford switch. Not that terminal 3 is not used in the Ford diagram.
The hand written diagram on the right side of the page is the wiring needed to install the inertia switch.
note that terminal 3 is used and connects to a light to indicate that the inertia switch has opened and will need to be reset.
I used an 12 volt LED light from Radio Shak mounted on the panel next to the switch used to disable the inertia switch
if you do not want to run the electric fuel pump all the time.

The image above and in the link have been changed 6-20-07
The image above and in the link have been changed 11-2-2011

For a switch the abreavations are C = common contact and NO = normally open side contact and NC = normally closed side contact for the switch.

The fuel tank unit in the middle left side of the above electrical diagram is the fuel pump, and the inertia switch just to the right of the fuel pump. The normally open contact of the inertia switch is not used in the diagram. I included a hand written diagram of a simple connection that can be used on an older truck or car. The normally open (NO) contact (3) of the inertia switch can be used to turn on a small 12 / 6 volt light on the dash so the driver will know if the inertia switch has opened and need to be reset before the car or truck will start. The link below will open a page with a large electric diagram that is shown above so you will be able to read it with out a magnifying glass, but the load time for the large diagram is long so be ready for a wait before printing. Make sure the inertia switch is in series with the fuel pump and on the hot or 12/6 volt side as show in the above diagram. The inertia switch has to open the hot lead going to the fuel bump to stop it during an accident.