Thanks for the interest !
Re Ardennes block, I will be going back to see the owner in a couple of weeks and will take more photos and measurements etc but I don't have all the info to hand
And on a similar theme, I was chatting to James Parry about this as well and he was saying how different the engine castings were on Augusta/Belna cars. Different webbing, bell housing shape etc.
We know that there are lots of other differences between Aprilias and Ardennes - door handles, gutter profiles, lights, bumpers etc etc so we shouldn't be too surprised and as Norman Stewart once said:
"There is no such thing a standard Lancia"