Search for Mario Konig. He has a few threads here with his info. He makes the mounts. There are also a couple other versions. TRD made a poly version, and I beleive once of our sponsors also made a polly version.
Because not enough people could support the market. That would most ikely be an expensive part. We do not have a lot of parts in our market just cause their market can not be supported by such a small demographic. To have things like that, you will need a shop to custom build it, and it will not be cheap unless you have connections.
Just a theory on the benefits of widening the rear track. Could the wheel being farther out act like a larger lever on the suspension? In effect making the suspension softer in the rear and thus inducing a counter-acting effect on the understeer on the front?
Also does anyone know the spring rates for the Whiteline Springs?