Quote Originally Posted by Dave Severson View Post
If it is the 9 3/8", they do fit into the standard 9" housing, might have to grind a bit on the housing for the ring gear to clear, but that's about it.
I think all you have to do is grind a relief the gasket flange of a 9" housing to fit a 9-3/8 ring gear(or so I've been told) I also think the 9-3/8 are all 31 spline, but, again, don't know from experience, only hearsay.

My recollection is that most of the 9-3/8 gear ratios 'suck', i.e. 2.56/2.69 or thereabouts. Great for prairie cruising/economy behind a C6 in your 429/460 powered Town Car or Thunderbird but not much for performance