There were a fair amount of shared components, but inboard of the uprights was unique to the M12. Also the engine mounts backwards in the Vector as compared to the Diablo. It's why the back of the Vector is so long. The transmission on the Lambo mounts mid ship where the ZF in the M12 is behind the V12. The chassis are completely different.
Losing the lambo engine deal was the killing of Vector in the M12 era. When Lambo was no longer obligated to sell engines to Vector, they stopped and tried to forget that it had ever happened.