I dont want to buy a rebuilt one, I want to rebuild one myself, because I need another project to take up my free time and my current 4.0 is going on 200k. I know it is a time consuming process, thats why I am thinking about picking one up from a jy or off of cl. and rebuilding it while I still drive the yj, then once im finished Ill put the rebuilt one in the yj, and if worst comes to worst and the rebuilt one blows up or somthing crazy, I still have the old one to put back in. This will be my first time attempting to rebiuld an engine. I am pretty knowledgable on engines ect. I am going to school for auto technology, so I have most of the skills and tools to do it, and when I run into trouble I have many connections to help me out. But thanks for the input and info.