Timing belt keeps slipping when it does run it will bog down and die after a few miles. New fuel filter, pump and pressure regulator also new timing belt and plugs.
I don't understand what you are saying, If the timing belt keeps slipping it won't start at all. If the belt was replaced then if it was installed a few teeth off then you will have trouble starting and running the engine.
Did you change the timing belt because it was bad or did you change it for maintenance reasons?
I need more information on your truck like the year, engine size, what is the fuel pressure, did you take a compression test and if you did what were the readings?
A compression test will confirm if the valves bent when and if the timing belt went bad. A low compression test on all the cylinders with a dry test and a wet test (oil put in the cylinder) will confirm bad valves.
If the belt blew then it is possible all the valves bent when the engine stopped.
Get back to me when you can with this important information.