Just finished about 2 weeks ago doing a few mods to my 350 to get more power out of it. I left the block in the truck & didn't do anything to the bottom end. I put on a set of double hump heads, new cam & lifters, new timing chain, & a new aluminum intake. I am real pleased with the power gain that I got. I went yesterday for a little trip thru the woods, after about 2 hours of riding I started hearing a noise that nobody likes to hear, a little man with a hammer inside my motor ! I am not sure which it is but it is either a rod or main bearing. So now I guess I will be pulling the motor out for a complete teardown and rebuild. I guess the lower end just couldn't hold up to the added compression and power. Oh well this will be just one more project to add to my ongoing and never ending list of things to do.