Gene, since the timing isn't right for you to tear down the engine at this time, and you aren't having overheating problems, and if you don't use the truck as a daily driver, you can get away with running it as is until its time to tear it down to make it like new. Poking a wire in the drain hole until something moist comes out will make you feel better. At one point for 18 years, I was in your shoes and vowed not to do anything until I did everything to it. Just keep an eye on the engine temperature gauge. Most of them don't run hotter than the "0" on the 180 mark.
Carl
