The TON Fiesta ST uses the stock engine with tuning from Mountune, Sadev (I think, as they have used a couple of different transmissions) sequential 6-speed, and the suspension and brakes from the MSport Fiesta R2. The ST shown in the videos was a production Fiesta ST that was modified at Team O'Neil for Rally America competition. So far, the Fiesta has won 3 Rally America 2WD National Championships. The first with Chris Duplessis, then with Branden Reeves, and last year with ACP using the ST. I think there are at least 3 different ST's competing in 2WD this season. Every race there are more and more Fiestas running!
If you want to learn to rally a Fiesta ST, Team O'Neil has a number of the left over Fiesta Movement ST's along with the original Fiesta Movement cars that they use for the rally school.