Tuning at 435 vs 440 vs 442
 
In my personal opinion leave the instrument at original pitch..
 
An analogy I have to offer using singers.
 
How about cutting a basso into a tenor, or a baritone into a countertenor
Things start to scream and screech at the top end.
 
I suppose you could move things up and down in the holes and change
the pressure..
 
But you no longer have an historic instrument...
or
encourage everyone else to change their instruments and yours will
be one of the few intact ones.  It'll make your organ more valuable
as a preserved historic object
 
Kevin Douglas Chun
The Curtis Organ Restoration Society/ U of Pa