Last time I heard, it was a bunch of hooey. They have not made the adaptor for 5 years and it was not a seller so they are not going to remake anymore.
That is the same problem that andyf over at ar engineering had with his factory based slant to small block adaptor. Their just wasn't enough interest in them and that was based on using a mopar trans in a mopar. If you are interested in the a500 swap username "dusteridiot" over at slantsix.org has the cad program and can tell you more. If you get on arengineering's website you can see a good picture of the slant adaptor that they used to make.