Lippy, what's the distance between the rear end mounting uprights? The standard these days seems to be 16".
It's hard to tell from your pics but the point where the bars meet on the rear end mounting upright seem a little high compared to what I remember on my cars.
I wonder if you lowered that point if it would help your problem?
I would ask Keith Burgan, "Roo man", at the CFC board about this as he has many years experience with chassis building.
Check out his ad on this page
http://www.nostalgiaprocomp.com/sponsors.html