Good luck.  I know of only two companies building large movements:
Porter does disks, and Reuge does cylinders.  Neither wants to sell 
the bare movements, because the money comes in when the movement is
combined with the expensive box, and the price goes through the roof.

For large movements:  Your best bet is to hit one of the MM marts and
pick up an antique movement that has lost its box somehow, or one with
a box that isn't worth restoring.  They aren't too hard to come by, but
you will need to find one already restored, or be prepared to do it
yourself, or wait to have it done.  Or you can do what Charles Hind did
and build your own from scratch.  It's possible, but it's a lot of
work.

What you can buy off-the-shelf:  The largest movements available that 
I have found are all from Reuge, but they are smaller than the antique
style you are talking about.  They have 72-note cylinder movements --
they can be very, very nice -- but they are not really competition for
a glorious old antique.

They also make two disk movements: one is the 4-1/2" inch movement 
they bought from Thorens (which is likely too small for what you are
describing), and the other is the 11" Reuge/Thorens, which _might_ be
borderline big enough.  You can get any of these from Nancy Fratti,
*but*,  she tells me she has had really poor luck with the 11" model:
they frequently need work right out of the box.  But that is the
largest disk-type unit I know of.  For more info you can contact Nancy
at (518) 282-9770.

Regards,
Larry Smith