I have worked on many trucks and SUVs of this platform. I know how these fuel pumps fail. Most likely the wire harness shorted out to the pump. On most occasions this happens in the tank. To fully check out this hack job you will have to drop the tank and inspect the pump bucket. If you can say its good and a easy fix, next is why the lights do not work. There on a different harness and I don't see why that would be cut.
You will also have to make sure that 2/4 drop was done correctly, otherwise you will have front end problems, driveline vibration and may have driveline problems.
If this all checks out, next is the normal stuff; checking the engine, transmission, and being down here A/C.
Be aware that occasionally on the 4.3l the intake gasket needs to be inspected as they fail. It's a easy fix if you do it yourself. Injectors are another known issue.
Not trying to deter you from this swap( an even one at that), but to be sure you know what your getting into. If we were closer, I'd come look at it. Remember, there are plenty of vehicles out there and you don't NEED to take that one.
Sent from my overly sofisticated electronic device.