Supercar_Kid and olredalert;
You are welcome. It came about as a product of my research. I cannot guarantee I am 100% right, but all the evidence fits.
On the 68 and 69 Novas the Fisher Body sheet does include the big block codes. Which is kind of odd. The Fisher sheet would only include RPO codes for options that the Fisher side had to worry about. Dual Exhaust required an extra mounting plate. Manual trans would require a hole in the hump. A console would require a mounting bracket. The hard and soft trim whether it was regular or deluxe. Custom options and SS trim also required Fisher work. I am not sure why the engine mattered to Fisher. In 1970 the Fisher sheet switched to a card tag and the RPO codes disappeared. In 1970 before the cards it looks like they dropped the Engine codes.
You are correct about the commonality of Fisher Sheets. 99.9 % of the sheets found in Novas are Fisher sheets. I have heard more about Chevrolet sheets on Chevelles and Camaros in that order.
The Chevrolet sheet is the ultimate find. It lists all the codes including the engine codes and suspension codes.
For everyone hunting for a build sheet, I wish you the best of luck. Send me copies if they are for a Nova……
Greg Roberts