FYI, the intake Ryan posted pics of has been modified, there should be 4 individual holes under each carb, not one big one. Here's a link to an original that hasn't been modified
70-71 Hemi Intake There is a bit of overlap as to what features identify the various years because engine part inventory was not first in first out, Sometimes an older revision made it onto a later engine. That said GENERALLY speaking, you want to see the larger "P" stamped to the left or above the big Pentastar as well as the casting irregularity that Tony D. mentions (due to a mold casting repair done in the top of the #7 runner around 1968-69). Most original 70-71 Hemi's I've seen had one to the left as the one in my link and Ryans example does.