In general, manufacturers are seldom interested in restorations of old products as there is very little money to be made in this area. Also, for high-end bikes there is a concern about counterfeits and fraud using original NOS decals. In fact, you often can't even get a paint code from a manufacturer, as they consider this copyright material in many cases.
The only large shop that I know of helps with classic restoration is waterford bikes - they are still refinishing paramount cycles and providing original decals or new runs of their original artwork. Custom shops such as Baylis Cycles or Richard Sachs can do it for their own brands as well.
The main sources for reproduction decals are (a) sssink.com in the USA (their coverage of MASI and Colnago is very good), (b) Nick At Lloyds cycles in the U.K (with good coverage of english cycles), and (c) Greg Softley in Australia (with coverage of a range of cycles including french cycles especially), and (d) J R. Anderson, wandson1@msn.com (high quality decals for selected british bikes.)
When it comes to parts, manufacturers do not have stocks of leftover parts, especially 40 years after production has ended. In fact, I think that many manufacturers clear their stocks of parts at the end of each year by selling them on the grey-market and so you wouldn't be able to get 1969 parts from peugeot even in 1970, in most cases.)
If you had say a 1969 bike that broke down in 1971, you would get 1971 parts from the parts suppliers, or via the manufacturer, and hopefully the same parts were still being made in 1971.
- Don Gillies
San Diego, CA, USA