There aren't standard threads on many of the shutters. I did try my Tessar cells but they wouldn't fit my particular Ibsor, they came in a 1931 Compur and also fit a modern Copal 1.
Sometimes pre-war 135mm & 150mm 9x12 lenses in good shutters sell for very reasonable prices $20-$30, or you can find 9x12 cameras incomplete but with a good working lens/shutter for about the same. I'll let you know if I see one.
The ground glass holders are quite simple, about the only thing that can need repairing is the fabric or the glass. I've jus had to replace the fabric on pre Anniversary Speed Graphic. Glass is very easy to replace but again they aren't standard so you'll have to measure the old one / and the sppace it fits in.
Grinding a new glass screen is quite quick and easy according to many people, and there are plenty of examples of how to make your own on the internet, you need to do a search of Apug as well. I have some Agfa glass plates that are ideal so I stripped off the emulsion, now they need cutting to size and grinding - I want to try for myself even though I'll buy GVB screens.