in need of serious help fast

i have a 96 blazer with a vortec 4.3 (w motor). I have this terrible knocking sound, so we bring it into the shop and tear it down, the timing chain had a lot of play that it shouldnt so i replaced that thinking it was causing the knock, didnt fix it. so i tear down the top end and i had 2 bad lifters....so i figuired ill be better off to replace all the lifters, pushrods, and rockers since its apart. i get it all back together and the knock is still there i have no idea where to even look next.....the 4.3 has higher miles, i hope someone has had this problem before and can tell me what to fix cause money is running thin now.....