Ive always heard that the early 9in from the mid to late 50's cars were the narrowest and also the cleanest looking. (ex: 57 ranchero ) When i was looking for a rear end i went to the junk yard and found some. They would have worked great for me but the guy wanted like 250 for it and it was missing something which i dont remember. So I ended up using a 8in because i didnt want to have to cut one down. Im building a 33 though. My brother how ever is building a model a and he used a 8in from like a granada and he didnt have to cut it down either.
You might want to look into a 8in. Your not going to tear it up either.