Believing it was the ultimate achievement ,one of my ambitions was to build a stronghold.
After much pleading to do so I moved to a clan that already had one.
It was there I found out having stronghold was only the begining,and not the end.
That being said you get stuck if you dont have one but it takes a lot of work, and this was in the days before all the upgrades to now level 5 were introduced.
From memory, as I can't check, the question you want answering is hard to define.
I think there is a sliding scale in the conversion buildings,such that you determine how fast or how much time the conversion takes, and this determines the amount of resources used.
I never got to learn and figure this procedure out for myself.