With all the chassis reinforcement pieces installed, the difference is astounding, no matter what suspension you have. Ever drive an E Body that makes NO NOISES?

I'm currently writing a series of articles for Mopar Muscle that will cover a lot of these topics. I also have a book on the way on the same subject but that won't hit the stores until later in 2011.

Your questions are valid and there are few vendors who can really help you. XV has invested a bunch of engineering time into their products. Firm Feel has 20+ years of Mopar road racing experience behind their stuff. I don't think you can go wrong with either vendor.

I am also not convinced that the aftermarket stiffened rad supports make any real sense...as well as some of the other products available to drain your wallet.

I have been flogging an e body for too many years now on the road course. I have learned a thing or two about what works, what doesn't and that you can handle really well without breaking the bank and still drive it home.

Unfortunately there is no handling forum so what really needs to be discussed won't happen here.

Again, the lower crossmember will help.
When you twist the car the front frame rails will point in different directions. The flimsy radiator support will flex with the frame rails.
I can see the evidence of the lower radiator support moving on my hot rod. It was tweaked a bit a few years ago. After playing with the TT440 and enthusiastic driving, the lower support has flexed and broken in a couple thin spots. I have to repair it before I put the engine back in.

A stronger lower tie bar would help the rails stay parallel and stop that movement.

It seems like a good mod to me too even though the weight hit is taken ahead of the front wheels. On a more serious road race car the frame would be tied together further back but that isn't practical on a street car. So the XV solution is a good compromise for someone who wants a car that still looks basically stock but works better.

The older NASCAR setups used a welded in K-frame to stiffen up the front chassis. That obviously works but most guys are not going to want to weld their K-frame into place.