Wow, what a mess!
Wish I could answer your wiring question. I've never had to do that. Maybe someone else here can answer that question.

 

I pulled out the pump today...
Here are new discoveries :-(
The cables and connectors in fuel pump assembly (in tank unit) are melt.
Pump connector in melt.
Cables from tank to body are burnt.
I think it was burning for long time.
You see this green staff on the copper (do not know English word for it). It appears after exposing it to moisture for long time.

Anyway, I am glad it happened. It could be much worst...

Now I will fix everything.
I am searching ebay for this cable.

Ivo

 

This story just keeps getting deeper, but it sounds like you have found the root cause of the problem.
Here's my theory of what happened:
The muck in the tank and I'm sure in the fuel filter and fuel pump strainer caused the pump to work harder to maintain fuel pressure. This would result in an unusually high amp draw that generated heat to melt the wire insulation, but not enough to blow the fuse until the wire insulation melted through, allowing bare wires to make contact with each other, hence blowing the fuse. The green tint on the wire is oxidation of the copper wire due to exposure over a long period of time.
You are lucky something worse didn't happen like the wires catching fire. Fortunately the fuel pumps are engineered to be intrinsically safe (explosion proof) so I don't think there was any real danger of the tank exploding.

This is just one theory,
What do you think?

 

Some progress here.
I almost rewire "new" fuse box. It was good find with all cables and the two connectors, so I would need only one cable splice
I moved usable old cables, the burnt ones were from big connectors to fuse box and some cable bridges in the fuse box.
Here comes a little problem.
I have to move two cables from this connector:





Can anyone explain how to depin this connector.
Thanks for the help,
Ivo

 

Just for the records, if anyone gets to this...
Delphi PA66 depin disassembly

It is very easy to open, use hook type awl, put it in tiny opening between housing and pry lightly. It should click and open. Repeat on the other side. Then you get access to the pins.
See the pictures.

Thanks,
Ivo

 

Thanks Ivo!

I didn't know that.

You're quickly becoming our master electrician...Lol

 

You know, misery teaches you

I am waiting for Haynes manual to arrive and check all the wiring before connecting battery again.

Can anyone advise on any of these fuel pumps:

New GM Intank Electric Fuel Pump Buick Cadillac Chevrolet Hummer Oldsmobile | eBay

GM Intank Electric Fuel Pump Replacement w Strainers Chevrolet Cadillac New | eBay

New AC Delco Fuel Pump Strainer with Installation Kit GM Vehicles ACD1001 | eBay

I have to order one. I am leaning more to AC Delco pump, but it is Advantage series, which are not as quality as I expect.

Any info on this is greatly appreciated.

Thanks,
Ivo