The later Gen-IIs had a power distribution box under the hood, 86-88 used fuse links inline with the wires. The best way to go about identifying where the fuse links are located is by referencing an electrical vacuum trouble shooting manual sold by helm inc (about $30, but totally worth it). Most are off the starter solenoid batt post. Need to check for fused power sources at the relays, and that would verify.
The fuel pump circuit is somewhat involved, the EVTM I described has the diagram for it. There are a lot of things that need to happen before the relay can turn on. ECC relay needs to be good, computer needs to power on for the fuel pump relay to function.
Could be a fuse link, bad ground at the tank, computer relay, computer, fuel pump relay, tripped inertia switch (in cab under carpet), etc..... Bad ground would go with the gauge, but try to do some isolation first as they may not be related issues.
Also make sure the small single ground wire from the battery is connected (computer relay depends on it).
Good starting point generally would probably be to test for voltage at the inertia switch. That way you can isolate where there problem is - tank or under the hood. You will want to either use a test light or analog meter. The computer primes the pump twice for about 1-2 sec each when the key is put on run, so you may miss these pulses using a digital.
You can further test the circuit at the diagnostic connector. There is a pin you can ground that will supplement the computers control over the fuel circuit, so that you can run the circuit all of the time for diagnostics.