I like the T Bird IRS, and have one for a new project just in the
planing stages. I have the whole clip with sub frame to allow
the entire thing to bolt up with 4 bolts. It is about 63" wide
hub to hub, but one company that make shorter alxes and upper and lower
control arms in 2 overall widths is factory five.
The Mark VIII has an aluminum diff housing and aluminum lower
control arms. Also any 8.8 posi will fit in the housing.
As far as ugly goes, just get your head into the coolness of
having any IRS in your car, and then look back at those solid
axle cars, and then tell me what you think is ugly.
Happy hunting
Paul