I have a 2006 trailblazer with a bad 4.2l engine. There is a guy locally that has a rebuilt 2005 4.2l engine, I can get at a decent price. I know the head changed between the 2 years. But what I am wondering is the shortblock assy. Is the block itself the same as mine. Where i just use the head and all other parts from my engine and put it on the 05 block. What is the deference between the 2. Any help would be greatly appreciated.