Stubborn starting question...

Mine uses only the original electronic distributor and mounts outside it on the firewall or fender usually, but it can also go under the dash so there is only the wires from the distributor and the coil wire visible under the hood.
They are full true HEI using the newer 8 pin ECU instead of the old 4 pin style, and are capable of controlling timing for EFI with Holley and Megasquirt systems.
They work great and you can get replacement parts anywhere on any day of the week in stock.
The parts are also really easy to change if ever needed, as they are plug in with weatherpack connectors.
The kit comes with everything you need for changing to HEI.

As far as reliability, I don't know because no one has ever had one fail. :-)
You can chk it out here www.classichei.com