Abarth was the exhaust to have in the early 60’s. I just came across this December 1964 ad. “Install a World Championship Abarth Free Exhaust System on your MGB”.
It’s interesting that at $64.50 the MGB-100 Abarth exhaust is more expensive than most of the other cars listed. An Abarth exhaust for a Porsche is $54.50, Austin Healy 3000 is $59.50 and an MGA is $34.50. They don’t show us the cost to outfit your Ferrari or Lamborghini however.