I doubt Fred Franz left a lot of written material because he was blind for the last 10 years or so and I think there was already a shift away from his style in the 1980s while he was still alive. He could still dictate and write things when he was blind but it seems unlikely he was building up a lot of written material at that stage and with those problems.
His style probably still influenced the green Survival book in 1984 which was full of types and anti-types, although the actual writing was perhaps done by others.
I seem to recall somebody saying that the Trinity brochure was the last publication Franz wrote himself or had major input on. It would make sense considering his long-standing interest in refuting the Trinity. That was published in 1989 just a couple of years before he died.