You have been given some real good advice. Load the car up, and take it to a reputable chassis man! You need the correct lenght on the 4 link bars for your chassis. Do you have the same problem with the threads on the wish bone? Ed wrote an excellent piece on 4 links, great infomation!
The wheel base maybe altered from stock with any chassis work. But not to the extrem you are speaking of. With the rear end problem you have. I would have to wonder if anything is correct?
I sent you a pm, I have some pics. that will show you what everyone is talking about.
Dave