I've heard tales that organizations are going back through old data sheets, and putting
them on-line. I think it's an Urban Myth.
There's no money in it for the manufactturer to go back and put all their printed specs
on the computer for something they don't sell anymore.
This has happened to me many times. A few times I successfully got around the problem
this way:
Contact Siliconix directly and ask for help.
When I get young engineers of the female persuasion, she'll ask for help from all the
older guys in the office. They'll fall all over themselves to go down into the basement
and search the microfiche your data is on, to show her how helpful they are.
Sad, but true.
I don't have any Siliconix data that goes back that far.
Good luck