Which one LQ4 or LQ9? What year motor should I be looking for my 2000 Silverado. How long would this swap take roughly? The reason I am asking is because I have removed the transmission; for vibrations that I have dealt with in the drive line since I did the T56 install. Also, the clutch has never been right because, of the 4.8 motor that it is mounted to and the spacers that were needed has everything f***** up. One of the things that I noticed with the transmission out is that the pilot bearing is loose/wobbly and the output shaft has some movement in it. I think that this is where my vibration may be coming from. Sorry for the long post, would really like to get back to driving this thing.

 

'05 or newer LQ4 has the stronger con. rods... LQ9 has always had them. LQ9 has flat top pistons resulting in higher c/r. LQ4 is a bit more common, typically resulting in lower prices, where LQ9 is seen as "elite" motor and sellers may tend to jack up their prices.
Basically the only differences, decide for yourself based on what your application is.

As for your T56 trans/clutch issues, I've got no clue, sorry.