I have a 1990 ford f250 4x4 with a 5.8l i have replaced the fuel pump, i have replaced the computer, i have set the ignition timing i have cleaned the spark plugs and replaced the spark plug wires i have put a new timing chain in and still this piece of **** dont run right???

I'm not a qualified Ford tech but if I remember right, those vehicles won't power the fuel pumps until after the computer sees signal from the distributor.
Does the truck have spark?

Change the fuel pump its faulty.

One thing that would affect spark and fuel pump power is the EEC relay.
I would start with checking that.
The spout connector should be in the harness near the ignition module. Its a connector with a plug you remove to set base timing.

Relay, ignition switch or pump its self( noT likely).

the only thing else to make it run is the ignition probably the ignition module

I would drop the tank and replace the pump. These types of problems are fire hazard.

try replaceing the ignition module its 9 times out of 10 for ford trucks

We are having similar problems. My husband replaced the fuel pump, fuel regulator and now it cranks but dies when you give it a lot of gas. He thinks the fuel injectors are stopped up. I read where one guy replaced the computer and fixed it and another one replaced the EEC. Check the relay contact and clean and check all grounding wires.

Fusible links will be under hood off of selonide, you will need test light to check because they will not always be obvious.

sounds like fuel pump is dead check for fuel at injectors