I read your post looks like you did a lot to try to repair this problem usually white smoke is a water problem first after you repaired how long have you let it run if the same muffler is on the truck the antifreeze might be trapped inside this could take hours of heating to stop the smoke. if you find this is not the case can you tell what cylinder is causing the problem if it smells like a sweet smell a would assume it antifreeze l would than remove the spark plugs and see if a plug look like it was steam cleaned at the tip see if you see any water in cylinder if not pull the rocker shaft off the truck to close the valves install shop air approximately 125 to 150 psi into one cylinder at a time remove radiator cap and let sit look to see if air is bubbling in radiator or over flow bottle for approx 15min if you do not see anything go to next cylinder if you find one that is bubbling or overflows out rad than that is the cylinder that is causing the problem possible cracked head.get back to me with your find.