How do you tell a 6.1 hemi from a 6.4

Can you tell the difference between a 6.1 hemi engine and a 6.4 hemi by looking at the motor. Is there a part number stamped into the block? Or other form of identification I could look for.

my 6.1 has "6.1" stamped on the block, but if it is just crank change, may be same stamp for 6.4

Thanks for the reply. I purchased a 6.4 from a dealer going out of business. The block is stamped 6.1 but I believe it is the same block that the 6.4 is made with. All the paper work that came with the motor is for a 6.4. I guess I was just curious to know if there is a way to tell. When you spend that kind of money it's nice to know for sure.