First off, let me state that I don't dispute that the symbol in the middle Glyph 7 is not the Mayan numeral for 74. In fact, I've based my latest batch of research on that assumption.

Anyhow, I've done just a tad of research, and I've found that there are 74 "relic-filled" tombs (information found at http://www.indians.org/welker/maya.htm) in a former Mayan site called Caracol. The only problem (and it's a big one) that I've run into so far, is that I haven't been able to confirm my research through the numbers.