8.75
The most accurate list I've seen:
An accurate 8 3/4" rear axle width list | For A Bodies Only Mopar Forum
Don't use a 7.25 rear for reference- they're different. This chart from Moparts compares them:
Edit: I wouldn't go by the numbers in this second chart, just posted it because however they arrived at their numbers, the 8.75 and 7.25 aren't the same. Take it for what it's worth.
The first list is accurate to every rear I've had the opportunity to personally measure.
The most accurate list I've seen:
An accurate 8 3/4" rear axle width list | For A Bodies Only Mopar Forum
Don't use a 7.25 rear for reference- they're different. This chart from Moparts compares them:
Edit: I wouldn't go by the numbers in this second chart, just posted it because however they arrived at their numbers, the 8.75 and 7.25 aren't the same. Take it for what it's worth.
The first list is accurate to every rear I've had the opportunity to personally measure.