I'm trying to find a lq4 block that is a direct replacement for a ls1. I seen listings but don't know what part number block I'm looking for. I know the early lq4 block had everything in the same place sensor wise as the ls1.

 

I am pretty sure all lq4 blocks will be a direct replacement except for the early ones 1999-2000 that had a longer crank. I also know the lq4 is missing one hole in the block compared to the ls1 for the accessory bracket. People just drill and tap them.

 

Any gen III block from 2001 to 2007 should work.