ECI is a more complete kit. Has all the fittings. Be aware that the discs increase your unsprung weight and is noticeable in the ride.
There was a 2# weight penalty for the disc setup I fabbed for my F-1. (40# vs the 38# for the original drum stuff I removed). There was a 1/8" reduction in track width. And absolutely way better and more consistent stops with the disc.The various disk brake types I have used on many race cars have usually weighed about HALF as much as a conventional drum brake per wheel.
Wilwood and Airheart were probably the lightest. The JFZ's were very light but only single puck on the front.
The last Wilwood 4 wheel kit I bought came with everything needed to convert an early Ford to disks including a mechanical disk parking brake system. It even had new aluminum front hubs.
The universal pedal system was really nice. It could be mounted either on the firewall or the conventional floor location. The pedal box has a mechanical front/rear brake bias adjustment also.
At the time, several years ago, the Wilwood kit was comparable in price to other complete kits.
There was a 2# weight penalty for the disc setup I fabbed for my F-1. (40# vs the 38# for the original drum stuff I removed). There was a 1/8" reduction in track width. And absolutely way better and more consistent stops with the disc.
I'm not a fan of Wilwood. Don't care for their engineering, customer service or leadership. I dealt with them when I was in the industry, at two or three points in my career.