My suggestion was to determine the performance that he wanted so that he could plan the configuration of the machine from there.
I have to disagree on the question of power though. The Vincent engine was in such a low state of tune that increasing power is relatively easy !! The 3 C's to start with , compression , cams & carbs ! The original comp ratio of 6.45:1 was side valve territory to cope with the deplorable fuel of the time , very small carbs , modest ports etc. Agreed this gives a nice soft , smooth power delivery , but more is easily available without too much compromise.
Compared to trying to substantially increase the power of a modern engine it's a doddle !! Inevitably the torque characteristics will be different form the original Vincent but maybe thats what Shaun wants , a road burner ! Maybe it isn't , it's his choice to make , but he's asking for info so the discussion process in this thread will provide that.