Regarding extended compasses:
Eastern Organ Pipes, located in the former M. P. Moller factory, can replicate historic pipework if you send them a couple samples from a rank. That said, certainly, they can provide pipes for an expanded compass.
Generally, to save costs, some have found, in some cases, that spare pipes, not necessarily matching the make of the organ in question, can be adequate. That's a practice I would use as an absolute last resort, if I absolutely cannot find anything from the original builder.
As for reeds, many have flue trebles, generally of Diapason type, but these are notes that aren't used that often. Way up in the top octave, there is less variety in pipes, among various stops, as compared to the rest of the compass, where you find pipes that are characteristic of their stops.
For example, take the first 49 notes of the following three 8' stops: Spitz Flute, Koppel Flute, and Chimney Flute. Respectively, you have a tapered resonator; a short, cylindrical resonator with an inverted cone-shaped canister fitted over the top; and the same is done to the Chimney Flute, only it's a cap, hole in its center, with narrow tube soldered over the hole. Notes 50 thru 61 in all three stops, more than likely, would be Spitz Flute pipes. The higher up you go in pitch, the less discernible the tonal qualities will be. Also, certain kinds of pipes can only be made so small.
At Grace Episcopal Church on Broadway, in Greenwich Village, Manhattan, their 1961 Schlicker has failed, which is why Taylor & Boody is building an new instrument. They say about 75% percent of the pipework is either silent or has lost their intended tonal characteristics. This is because the pipes are collapsing or sagging under their own weight.
Pipes are generally made of a tin/lead alloy of various ratios. I believe that antimony was not used in making these particular pipes in order to cut costs, or, if they were made outside the Schlicker Company, something else was used, which was a bad substitute for antimony. A small amount of antimony is, or should be, included in the alloy for stability. I've seen similar situations in 1960s Casavants where full-length reeds were bending. I was told it was European zinc.
I've seen a number of photos of the inside of the Grace Schlicker. One shot shows a set of wooden pipes. They looked fine, so that would illustrate that wooden pipes, if properly cared for, will out-last their metal counterparts. A 48-year-old organ is not the best example of longevity as we look at the comparison between wood and metal pipes, but it's what came to mind and I thought I'd share it.
At Methuen, the famous Walcker/Aeolian-Skinner/(and Great Trumpets from Noack) is an older example. 1 thru 5 of the 32' Principal is wooden and seemed in good shape when I was there about 10 years ago. The remainder, or at least some of the rest, of this rank is about 90% tin and are in the facade and you could see that the largest of these were crumpling at the toe. This stop dates back to 1862.
Wood is fiberous and holds better than a material that is malleable.