That's interesting, does the chassis actually have a 1972 date on it? The Sorado was obsolete by then, not even in the 1972 catalog.
However, it may well be one of those anomalies that seemed to abound around that time; I personally have a 2000S with an inspection sticker dated 1972, and THAT was also "obsolete by then, not even in the 1972 catalog"...
Anyway I can't currently help you with a schematics for that particular amp but I have attached a schematic for a 200S, which should be virtually identical to your amp except for the SS rectifier.
Somewhere I have a CD with pretty much every Sunn factory schematic on it, but I haven't seen it in years. If it shows up anytime soon I'll post one for you, but in the meantime I hope this one helps you out!