Good luck with your 9" rear search. It's reputation speaks for itself. Especially if cost is no object. Even if you buy one for $100 from a wrecking yard, by the time you rebuild it, put a posi in it (or rebuild the one it's got), narrow it, put disc brakes on it and buy new axles for the narrowed housing you'll have somewhere between $1000 and $1700 in it.

That's why I suggested the Explorer 8.8". It's plenty strong (the upgrade to 31 spline axles is one of the few the Mustang guys have to do to make it live in 10 second drag cars). Supposedly it also has less rotational resistance than a 9".

Unless you're putting 800rwhp to it, I'm not sure the additional expense is justified.

Just my .02

If you do look through those 9" rears, I think the '79 Lincoln Versailles is about the right width and has factory disc brakes. Search this site. It's all been covered before.