The biggest problem in making this replacement would be the top action
(pneumatic stack).  The bottom mechanism probably would not be a prob-
lem.

The divisions between the breaks in the top pneumatic stack would be my
biggest concern.  The other is: Will the Welte stack fit precisely in
height and width?  Usually not.

I once encountered a technician who was very proud that he finally 
accomplished replacing a top pneumatic stack.  Somehow he did not real-
ize the bass section was one note short.  When it played, the bass was
a half-step off from the mid-range and treble.  Since he was tone deaf,
he did not hear this. I told him he could re-tube it to play correctly,
but he said it sounded fine to him.

Bruce Clark