I have a 1991 K5 with a 350 and just pulled the top end off to find what was making all the noise. Much to my surprise it has roller lifters, and not like any after market ones that I have seen. They have long connecting sleaves between each pair, and all of the sleeves are all held in place by one spring plate attached in the bottom of the gallery by 3 bolts. My question is: Is this a factory roller engine that just happened to make into my truck, or did somebody mess with it? The noise is most likely the bottom end, and I am not going to mess with that, so it is time for a new engine (170-200k mi. on this one). AutoZone has a rebuilder that offers both a flat and roller cam. I would really like to replace this one with one that is just as good, because I have been spoiled by this one's power and smoothness. Hope I can scrape up the $$ before it throws a connecting rod 100 miles from a tow truck. Thanks.