perhaps you're set on wiring it this way... but it is easy, very neat, safer from corrosion and involves no hacking or splicing....
you can make a standalone harness for it. power for relay from #30 stud in footwell, ground from footwell, add a relay 53 into the relay panel, add a fuse into an empty fuse location, run a little wire with ring terminal to fuel shutoff solenoid, and then then 2 wires from relay back to pump. all inside the car, no messy loose wires under the hood with chance of corrosion...
if you have a crimper and some new terminal ends (very cheap on mouser, digi-key etc), you can make this mini-harness without even a single solder joint