E Brake Cable Routing

Any tricks for fishing the cable through the frame box area? I am having a bear of a time getting the cable through there. Easy enough to get the threaded end and the cable portion through but the cbale sheath with the snap in clip is not going. I have A 70 Dart Swinger. Thanks!!

<Update .... With a bore scope, a little die grinder work and some minor sheet metal bender I was able to modify the opening to the point where I could fish it through>