Don't mean to come in the middle of this...but we know the driveline is garbage. There is no grey-area. We also know in this age of cost-cutting BS that the driveshaft is a POS. Clearly Ford is aware of the problem...but it comes down to $$$. It would cost millions to recall something like that.
I'm not on an anti-Ford rant or anything because for the most part, they build solid autos. I love my Mustang. My MT82 isn't the prettiest girl on the block, but she puts out when I want her to.
I'm just simply tossing my 0.02 in here by saying the driveline is a weak point on these cars. Even 100% stock ones have problems (DS, transmission, etc). Hence...as others have stated, if you're going to mod your car, make sure you have the cash to back you up in the event something explodes.
I am not arguing the issue of the drive shaft being underrated, out of all my 70's cars I have owned (5 of them cougars from 70-73) never did I have a DS blow up stock. Granted they were huge hunks of steel =)