Tim, sometimes stuff is "free" for a reason! They might be worth exactly what you pay for them!

Based on your expanded description, those were probably bolted to a bracket that was welded to the housing. Still ends up a rigid connection. Perhaps the reference to being a "street" version means that they used rubber bushings at the points where it was bolted to the axle bracket, but that still wouldn't give you enough compliance.

Looks like Mike was typing the same time I was. Since he knows more about this stuff than I do, I'm glad his and mine were so similar.