Well I definitely think you voided the warranty, so can't take it back to the dealer now.
Sorry, if I'd seen the other thread I would have told you that it definitely wasn't in the ECU. Everything in there is solid state, nothing there to click. That audio sample doesn't really tell me much, no spatial relation for me to judge where it might be coming from. If I were sitting in your truck and heard it that might be an entirely different story, I'll come listen to it if you want to buy me a round trip ticket from Atlanta, GA (didn't think so, don't have passport anyway). From what I could hear in that sample it sounds more like something loose and rattling. It could be a relay though, IIRC as I was tearing my 86 Ranger apart there were a few relays up behind the dash in that area. I'd actually be inclined to think it was outside the cab, possibly a bushing somewhere in the front suspension.