I don't know where to find 430W parts, but thought I'd answer just o that I can follow this thread and if we find a good source of old parts it will help everyone. Gotta be some. There are a lot of old of JDs being restored.
I see in the business magazines that there are even some outfits doing complete rebuilds on the bigger JD ag tractors from the '70s. Apparently they were so innately rebuildable that a worn 4030/4050 100 hp tractor can be refurbished at a competitive price to new machines.
Ours 1958 John Deere 530 is the same vintage as yours, and was stock for 30 years and then we added a JD wide front & FEL some 40 years ago....Both upgrades simply bolted onto existing frame lugs. It's a marvelous machine. I'm currently beginning to look for parts to finish a long overdue clutch & brake job on it, but other than that it is fine.
In fact, it hasn't changed noticibly in the last 40 years, and back then any parts I wanted were as close as the local dealer. In 1990 when I went to buy a tach/speedo, tune up and carb kits & some gaskets plus that bizarre automatic fuel tap - the dealer had everything in stock! Perhaps it helped that the 530 shared many parts with the B series. Those parts have to be out there somewhere. Does the 430 share with other models? With the M?
In summary, I don't know where to get old parts because the 530 hasn't needed much. But hopefully we can both find a source.
Good Hunting,
rScotty