Well into the 90's, it was still possible to order a frame with features as desired. If De Rosa had the parts available, they were more than happy to build it to your specification. I went to the factory in 1988, was measured up by Ugo and made specific requests such as flat fork crown and specific seat stays. The frame was very close to a stock geometry but did have the specifications that I asked for. They did mess up a bit with the requested paint scheme, but all was fine as soon as I took teh bike out for a ride.

My two 1960's De Rosa frames have many items that are different one from another.

I think that attempting to make a timeline for non production frames is foolhardy. This is not like Colnago which is for all effects a production frame that is farmed out.