I second the AntiquePedalHarps group, though it’s not very active. But there’s a fair bit of knowledge on there:
You might also contact Mike Parker:
and Tacye Phillipson, who posts here and may see this thread. She’s done some impressive-sounding restoration work.
I have an 1837 Erard Grecian and the music school I teach in has an 1818 Erard Grecian – both of these harps still have their original soundboards. Another friend here has an Egan dating from 1835 – all three of these instruments are in full working order with good pedals.
What a great idea! I’m putting a tracer on this thread so do please keep us posted.