Not tryin' to crash the party but to the best of my recollection (I was a couple of years into my passion for racing at the time, about 10 years old) there was a bunch more than three built. And they weren't all that successful as they were known to be a nightmare in the handling department (they were not designed for racing from the get go).
edit: 'just googled and even Wikopedia has this info...
Last edited by jimclark; 03-09-2016 at 06:11 PM.
"Those were the days my friends. We thought they'd never end..."
jimclark