273?

A 8 3/4 rear with a 3:23 would be common. Just depends how it was ordered. Most GT's came with the good rear and the standard 3:23. A 270 model with an optional 273 may have a 7 1/4. The option books are a bit sketchy. They list the
7 1/4 until 1974 but don't list them past 1966 in the option charts. I'm sure there's an expert here that can help you. tmm