The engine number will tell you the year. If yours still has the sticker on the RHS head the engine number will be there. If the sticker is gone, the engine number is stamped on the skirt of the block on the LHS just above the sump but it's almost impossible to read without a camera of some kind.
There are other clues that involve removing the inlet manifold: once the manifold is off it's easy enough to discern the 2008+ "Eagle" motor by the shape of the ports in the cylinder head and the presence of the solenoid for the VVT cam phaser right at the front of the block.
See the last post on this thread for an example of how to decode the gen 3 hemi engine number:
There are other clues that involve removing the inlet manifold: once the manifold is off it's easy enough to discern the 2008+ "Eagle" motor by the shape of the ports in the cylinder head and the presence of the solenoid for the VVT cam phaser right at the front of the block.
See the last post on this thread for an example of how to decode the gen 3 hemi engine number:
