Is there anywhere that still sells the 3400 j-body swap mount?

I remember seeing a blueprint for one a while back, but I can't find it. If I had at least that, I could make one.

Any help appreciated.

I know your question is a few months old now, but wanted to let you know what I have found out.
If you haven't found one yet and are not in a real big hurry to get one, you can contact David Hill about buying one. He has a few ready to weld up, but hasn't had the time to get them finished yet. He will put you on the list and get back with you as soon as they are ready.

You can find his contact info in the last post of this thread:
http://www.v6z24.com/jbodyforum/3400-3500-mounts-black-friday-cyber-monday-sale-t109634,start,255.html