Don't forget that there are also some Powerglide transmissions out there that were designed for 4-cylinder Novas. Those are identifiable by the presence of four fairly large holes (2"?) drilled in the bellhousing, two on each side. I believe that they were not equipped with an external transmission cooler and the holes served to bleed heat off the converter. Also, if memory serves correctly, there were some early Powerglides that had a shorter tail shaft and housing. I have found those in the X-frame, full-size cars, pre-1965.