Conserve not restore.
It will look better that way with all its history on show.
Just do what is needed to keep it going.
Possibly do the paint if it bugs you.
BHP differance may be where it is actually measured ie rear wheel, sprocket, crank.
All will give you a different BHP.
Also may be different way of measuring SAE DIN ect.
Another may be manufanctor quotes which may vary greatly from reality.