Unfortunately the info was supplied to me on a 'no tell basis' as the man concerned makes his living by engine prep (not vin's - which is why he told me (and I was spending money there at the time!)) and its something that 'paying customers' get. The man's stellar reputation in engine prep is well known.
What I can say is that the engine concerned was a 500cc OHV single derived from the late 1950s/early 60s period of manufacture. The springs are not originally from a motorcycle engine, but their data was derived as a direct consequence of a large european R&D budget for endurance racing!
That probably doesn't help, but is all I can tell without breaking my word.