Original Rear end type on my 70 Duster

It’s just definitions!

On a base model the 7.25 was standard unless other options were specified.

On a 340 car the 8 3/4 was standard. Not exactly a “base” but they were broken out separately

Since we were talking about a 318 car to begin with the “standard” reference doesn’t make a ton of sense, the 318 wasn’t the standard option already. Maybe the default with just a 318 and no other options was still a 7.25”, but an 8 3/4 was easy enough to have, it was just another option on a car you already had at least one option on…