I'll bet it had a lot to do with cost and complexity. I've also heard that the IRS cars are harder to launch that the live axle cars. I still think it should be an option though.
This is true...theyre also stronger and lighter. One more reason why the Challenger and Camaros are heavier than the Mustangs.
FWIW, I have 15,000 miles on my BBP 5.0 GT and zero complaints about the solid rear axle. I also have 250,000+ miles under my belt (including many autocross days) in IRS sports cars so I'd like to think I have some worthwhile perspective on this topic.
Yes, on bad pavement, the tail can get upset and the solid axle becomes a problem...but horsing around on bad enough pavement to make the problem obvious is a very dumb idea anyway.
