The 1.6L Kent. Great engines - I had a collection of them when I owned two Mk1 Fiestas and a Formula Ford. There's no way in hell that a N/A 1.6L Kent in anything is faster that a FiST. I had twin Webber 40 DCOE's, worked-over heads, a lumpy cam, headers, and a tuned exhaust with those loadable muffler packs at the exit (I forget the name) on my street-A/C car. I'll bet that I wasn't making more than 145hp up way high and near nothing down low. For the time, it was a killer hot hatch and sounded like a pissed-off motorcycle. I'm 100% sure that a stock FiST would just walk away from it. Fast is relative.
Track only, loosely-built, rebuilt every season, high-dollar Kents with steel cranks and unobtainium pistons pressing way over 12:1 with 45 DCOEs make 180hp. Sure, the FiST is a *lot* heavier, but it makes torque way, *way* earlier and longer than a built Kent. And I'll bet that a 180hp Kent (engine only) will cost about the same as a 2015 FiST (the whole car).