I've searched and searched to find the correct wiring harness and I'm seeing different results everywhere. I don't know if I'm supposed to get the Metra 70-1721 or the 70-1722. I've seen sites say the 1722 is for 06+ Civics and another say 06+ Honda. Meanwhile the 1721 usually says 98+ Honda. Please help.

 

while I don't have an '07, many threads have indicated that ALL years
are plug-n-play compatible/interchangeable, which makes sense because
the s2000 still uses a single-DIN unlike most (all?) other Hondas which have
gone to integrated headunits. So it would be the Metra 70-1721.
I will caution you that if you plan on using a DCI to retain your dash controls,
many harnesses don't have the two s2000-specific wires for the dash switch
and mute switch. Unless they've changed it in the last few years, the Metra
doesn't. If you are buying a DCI from Modifry, buy his harness too which
does have the wires.