Cantina Colli Novaresi: This was a cooperative with many members. I'm not sure if it still exists, it may well not. "Colli Novaresi" are the hills that encompass Ghemme, Fara, and Boca in the Alto Piemonte.
Produttori di Carema: Is the cooperative in Carema, and basically the other source for Carema besides Ferrando. They still make wine currently. I've had good luck with older bottles. But keep in mind that 64 and 74 are both relatively light, if respected, vintages. This coop has a tendency to chaptalize, I think. There used to be the red label bottlings (normale) and the white (riserva) bottlings back in that time frame.
Dessilani: This was the big producer of Fara in terms of volume for a long time. I was recently told that it no longer exists, owing to being involved in some sort of unlawful blending scandal. I've only had bottles from recent times, not from the olden days. They were likeable, I guess, but rough hewn.
Negri of course still makes wine in a somewhat oaked up style in Valtellina today. Good vineyards at play. I've never gone back to the 80s.
There are two producers with the name Nervi. As the mention is made of Spanna, I think that the offer is for Livio Nervi, which I don't think I've had. Luigi Nervi is the more famous Nervi.
Travaglini still produces today. Think of the the oddly shaped bottles and the high yield crops. I've never had a great bottle, but then I haven't gone that far back, either.
Vallana is of course the legend. Still in service, although not what it was. What it was - in regards to blend - being a subject of debate. "Campi Raudii" was the "rotten plain," where thousands of bodies were left to rot in the sun after a famous Roman bottle on the site. I've had quite a few old Vallana wines. Check brooklynguy's blog for a write up of a dinner I hosted. The Vallana back vintage wines are getting more expensive, and these are decent prices. But alas, there is no '55 vintage here.
The other producers I don't know myself, and would only be quoting Sheldon Wasserman on. I would suggest that if this is a subject you want to learn about, that you pick up a copy of Sheldon & Pauline Wasserman's "Italy's Noble Red Wines" 2nd Edition (I am unaware of a third). That is the bible for this sort of thing.