my truck has no spark

most likely the ignition control module, the thingy that screws onto the front of your distributor. It takes a special tool to get it off, most parts stores will have it, but you will have to loosen your timing clamp to move the distributor so you can get the tool in it, so make sure you have a timing clamp wrench, and then you'll have to re-time the damn thing so make sure you have a timing light also. mine resulted in 4 trips to get all the stuff I needed.

i already replaced it and i also replaced distrubutor cap&rotor,ignition coil,wires,sparkplugs,new battery

Any fuel pressure when cranking? If not, the problem is a bad crank position sensor.