booster addition to manual brakes

Swingerman
Stop thinkin out loud. lol
The brake lines only have to connect point A to point B. And since they end at the frame rails, only the soft lines need to be changed. That is; the flex hoses, commonly called rubber lines.
But you do kinda bring out a point;to keep your eye on the big picture.
Going from drums to discs requires a mod to the M/C(namely the removal of the Residual-valve to the front brakes), and possibly different P-valving. And going from non-boosted to boosted can (personal preference)use a different M/C again.
And I know nothing of right-hand drive cars.