I used the 21 circuit one in my truck and other than making a couple of small 'adjustments' to conform to European specs (our stop/turn signals are different) the turn signals must be separate,it was a no brainer.
Although i've since found out I could have left it 'as is' on a vehicle this old.....

Like the guys mention and I'm sure you already know,they're marked every 6".
Just pay attention to getting good grounds (most electrical fault can be traced to bad earthing)