My first post was a bit of a fishing expedition to see if the answer changed. Years ago when I asked this question, I was told that '64-66 Pontiac rear ends were 60" drum to drum, and '67-72 pontiac rears were about 61" and change wide drum to drum.
The '64-67 Chevy rears were narrower and got wider in '68-72. So yes, the '68-72 Chevelle 12 bolts will be approx 61" wide. Not the path I've taken in this deal, but to each his own.
https://forums.maxperformanceinc.com...d.php?t=416764