When no power is applied to the relay 30 is connected to 87a:

When power is connected to the relay's energizing coil (85, 86) 30 is connected to 87:

Place inertial switch between relay out (87) and fuel pump +.

In schematic above (JamesWnew's post) the terminals for the FP relay shown are:
Left - 86
Right - 85
Top - 87
Bottom - 30
(87a not used)

 

This is what I did. I installed a oil pressure switch and an inertia switch. It is simple.

http://www.cardomain.com/ride/3899808/1968-ford-mustang/page-7/

 

Just to confirm I understand.....


Battery to 30
Ignition to 86
Ground to 85
87 out to the inertia switch

another question.....is the inertia switch always after the relay?

 

Just to confirm I understand.....


Battery to 30
Ignition to 86
Ground to 85
87 out to the inertia switch

Correct

Put a 14 or 16 AWG fusible link (or a 20A fuse) on the wire to 30 where it connects to the battery (usually at the starter relay Bat+)

another question.....is the inertia switch always after the relay?

That is how Ford does it.

 

I put the inertia switch before the 12V (in) to the relay. Thinking if the inertia switch trips, it will kill power to the relay and shut off the pump. Either way should work I guess.