Hooked a 65 Barracuda

May be that the cable is just unhooked! Check both ends, if it is the original cable it should screw right in to the speedometer! May be that the problem is at the trans end because it is a 727, your early cable probably won't screw into the speedometer location! Maybe a message to member "65Dartman" Don, he had a conversion cable up for sale here a couple weeks ago, he may be able to steer you in the right direction!