I saw this one in action, at the portuguese rally some 25 years ago(or even more, I'm too lazy to find out the year).
It was HUGE, earth-shaking (literally, the sound of it was a deep roar) and a wonder to see go by - flat out - in narrow and twisty forest roads ...
Besides, it was a beatiful car in that silver and black livery.
The Group B M1 also made an apperence at the 1983 Rally Corsica!
The M1 was used at Pikes Peak.
These or the Lancia 037. I may find some more tomorrow.