Hi Adam, Carl Abarth was a man who liked to tune engines, after he was a POW in the 2nd world war he started tuning racing motorbikes, he was nearly killed racing one, so he moved on to car engines. He set up his won company and worked with many famous names including Ferdinand Porche, he ended up mainly tuning fiats really and became very well known. Fiat eventualy bought his name to trade with in the early 70's, and thats how we know of Abath fiats. just remembered C. Abarth wasnt actualy Italian he was Austrian by the way.
Fiat 126's were not produced or tuned to be abarth, but we can add abath components, i.e. particularly if they are aircooled engines like the fiat 500(no abarth bits for BIS's). 500's were raced for years and still are today. Im pleased you asked about abarth, i hope it answered your question.
Chris