Bly-
The adapter that allows the speedo to spin in reverse goes onto the back of the speedo and then you screw your speedo cable into it.
The "little metal band" is a "c" shaped clip that holds the driven gear (the plastic gear that goes in the tranny) onto the speedo cable.
And yes you need an o-ring.
You get the o-ring and clip from any place that sells mustang restoration parts. I got mine from Dallas Mustangs.
And as for the rest of it, you can put it . . . .
