Wouldn't the solution to this problem be to shoot only for a theatrical release print preservation (warts and all) rather than trying to shoot for what is/was on the negative?
You'd need to check against at least one good early '77 Eastman Kodak 35mm print to rule out any issues introduced by the TechIB process, but this should involve far less guesswork than trying to guess what's on the negative.
Just my 2c. Keep up the good work, Mike.