Good luck. I havn't been able to get mine connected either. 71-74 should be the same. They use the intermediate cable...1970 does not. The intermediate cable connects to the left side rear cable at the frame rail. It runs up through a bracket that's attached to the front cable.(the one attached to the mechanism inside the car) It then runs through an S-hook that clips into the trans x-member. THen it goes through a bracket attached to the adjustable rod that hooks into the torsion bar x-member. Finally, it runs back and connects to the right side rear cable at the frame.
My intermediate cable seems about 3"-4" short from connecting to the right rear cable. This is with the adjustment all the way out on the rod. The new intermediate cable is basically the same length as my original one. I think the covering around the rear cables is too long. If the covering is too long, when the cables are clipped into the frame brackets, that would pull the attchment ball farther to the rear.
I bought the kit from Fine Lines. They don't make the kit themselves. They get them from "The Right Stuff". I called "The Right Stuff" and told them my problem. I asked if they would make me a new intermediate cable that was 4" longer. They said no.
Then I called Inline Tube and got the measurements of all the cables in their 71-74 Challenger kit. Their cables didn't match the lengths of my original ones.
So...I'm thinking about making my own intermediate cable.