I cannot imagine what purpose the red wire has. Did they believe they were grounding the radio?

As far as NOS speedometer goes that's actually not expensive for NOS speedometer. They've gone through the roof lately. There's another NOS one speedometer on feebay for $250 and a used one for $60 which I'd never buy a used one, then one here for $140 http://www.dpmotorparts.com/list_parts.cfm?page=273 Here for $275 https://www.hiltopautoparts.com/pro...6-chrysler-plymouth-dodge-b-body-models/

No none of them are mine lol