mine are getting installed this week. be ready to spend some $$$.
I got polyurethane bushings, heavy duty cross member, Billet FLow IRS Brace to all be installed at the same time. then the MM subframe connectors will be on the week after that.
and definitly go with 4.10's if you arent doing a power adder anytime soon.
The FRPP 4.10s (part # M4209G410) are $179.95 or $184.95 for the 4.30s (part # M4209G430) at CJ Pony Parts, and they usually offer free shipping on Wednesdays. Don't forget the bearing kit (part # RPM2K) for $89.95 as well! You can also call Bill (the Cobra sales/tech) at (717) 657-9252. Tell him George Cradic sent you.
at one mustang i shop i got quoted for 700 for a gear install on my cobra, but i turned them down and had a guy put them in for free at the dealership i worked at. it took him about 5 hours or so to get it perfect.
don't pay over $400 for IRS gear swap. it took me forever to find a place who at least wanted to do it. a lotta mechanics are BS'ers and don't know anything about the IRS and try to tell you how difficult it is. well it's not hard if you know what you're doing. shop around. I've gotten quotes from $400 - $1000