This Illustration shows this wire running along the edge of the valve cover where it meets the intake and back into the loom. (bottom left image floow it back from #9 - indicates the sending unit)

It is a single solid Green wire as Vikki mentioned and will go into the main loom as it goes down towards the firewall at the fuse block... (And you'll need to make sure you have the sending unit for the light, and not the gauge)
Not usually a problem unless it's the other way around with Rally Gauges...

http://1968firebird.groupwhere.org./illustrated/elect/elect2.html (3rd image group down)

Maybe you'll get a better idea from this?

Brett - 67 Drop Top 455!