When we replaced a mid-90's Harken Mk2, a few years ago we went with a Mk4. No problems. I had a new forestay installed at that time, also.I have a Harken MKIV (Unit 0) on my little E26-2. It's an excellent furler. I have zero complaints.
Work is being done by the rigging shop so unfortunately I’m subject to his pricing for the h/w which is basically list I believe.Added one to our Olson 911 a few years ago, very happy with it. Best price I found at the time was through Binnacle.com.