the ends are supposed to be square they sit in the cut outs of the 2 halves. in the first pic where you have the centre sitting on half the carrier, is the carrier worn in the centre area? i dont have paint atm so i cant pin point it. there looks to be a fair amount of crap in there but the oil looks cleanish, was there much metal filings mixed in the oil, as for the noise at 60km/h it could be crown wheel an pinion or tyres, while the diff is out check the tailshaft uni joints if they're buggered they can make clunking noises.