Handbrake cable is 1 pc. It loops from each backing plate, around via the lever. You need the disc one.
The backing plates with the handbrake assembly, & discs will fit, BUT...

Regardless of which diff your VK has, you will need to keep your axles, as both are different to VL.

Buy a new rear wheel bearing set for a disc rear, and fit them to your current axles, with the spacer (salisbury) or unique disc rear seal (borg warner) and re-use your axles. They are also unique side-to-side in the B/W.

You will also need the hard-line off the diff, as they ends are located differently. This can simply be undone at the flex-pipe in the centre and swapped with yours.

But there's more to it.

The master cylinder for rear discs is different. You really need to change it. Don't be fooled by the internet idiots who simply claim you need to remove the anit-return valve - it's simply not true.

There's a different "crack pressure" rating on a rear disc master, and you end up with 2 problems if you don't change it.
1. The rear discs will never fully apply as hard as they should using the drum master.
2. The pads will drag & wear out fast (removing the anti-return valve cures only this issue).

You want to find a master from a disc rear car. VN-VP1 will bolt up, but you need to bend the LH front brake pipe to suit. This is the simplest conversion, as all VN onwards were disc rear.

The way to ID it is stamped into the front of the master will be something like C225. You want something with C2xx for disc rear, and C1xx for drum rear.

And if you want to get real fussy, disc rear cars have a different lower trailing arm - only in the fact they have a retaining clip welded to them - to retain the handbrake cable, but it's not essential.