I ran the XHD springs with Cal Tracs....... No problems.
I wouldn't try and use them with SS springs though.
Keep in mind....... The bars were available for quite a while before the split mono-leafs were.
My Cal Trac/XHD combo replaced some well used SS springs, and the Cal Tracs were much more consistent, although best-to-best, they were no better.
I found the Cal Tracs made the rear of the car quite stiff for road use.
If you can find any old articles on the Calvert bars when he first started selling them, you may see that he developed them on a Super Stock Mustang with a 4 speed. And he used really stiff multileaf springs with that car. When I remember that it makes me wonder why the change to monoleafs.
