I think you also have to account for the distributor drive gear, which from Performance Products are over $100. I know if this was my car and I was planning on keeping it for a long time, this project would be worth the time, effort and money. But since this car belongs to my aunt and uncle, who are not "enthusiasts" they are simply interested in keeping the thing running so they can sell it in a year or so.
No harm will be done by just putting on a new single chain and new rails right? And like I said before, this one has done just fine for the last 100K, so what's to say this one won't do just fine for the next 100K??