So I bought an ls motor not sure which one it is or what truck it came from and im in the process of building an motor the block casting is 1255364 want to know how to know how to identify exactly what year this motor is so I can move forward on ordering parts I know its lq4 I did pull the cylinder

 

Look at the casting Date on the block. It's on the front of the block near the top of the cylinder head on the passenger side. ABove where the water pump mounts. There are also date castings on the head if you pull the valve cover.

 

^^^ This ^^^

The code will look something like B160. That particular combo would decode to the 16th day of the Bth month (the 2nd, Feb) of a year ending in 0 (2000). A casting from about May or after would be for the following year model; they cast them, then "season" them for a few weeks to let internal stresses subside, then machine them, then build them into engines, then ship them to an assy plant to go into a vehicle. So about a 2-3 month, or more, process, usually. New models are in stores around Labor Day; assy plants usually change over year models in early July to support that.

 

Cant read the ones in the bl9ck and the head in dont see anything