Identification on used Mopar Crate 360

I am going to look at a slightly used Mopar crate 360 with the single plane M1 intake. From looking at their history I see them listed at 380Hp and 390HP. Was their any difference or just a revised rating? The bigger question, is their an ID on the motor to positively identify which version this is. Also where would it be located. I see that their was an old order number P4510851 and a newer part#P5153457. Thanks for any insight.