You can get a data cable from various suppliers including www.sea-tech.com
Putting insulators on the backstay is straight forward. I am told by a HAM operator backstay is more efficient up to 14MHz whilst a whip is superior above these frequencies.
You should use Times LMR 400 coaxial cable between radio and tuner and GTO 15 Cable between tuner and backstay.
Here is an interesting article on grounding
Apps for receiving HF weatherfax