Treblig, I like the idea of adding more rigidity in that area, but I am no mechanical engineer. I would like to add a short triangulated bar to the front of the subframe connectors to original torsion bar crossmember, but there's not a lot of room there unless I just use just a triangle piece of flat plate and weld it to the inside, bottom at the intersection of the subframe connectors and the factory crossmember.
For crossmember add-ons, I've always liked the look of the round tube type crossmember with the mandrel bends for the drop down at the trans mount with a flat tab to mount the rear trans mount, but I don't have the technology for that at home. I guess if I found a race care fab shop in my area the could make me up one, but this isn't LA.
Which rear mount did you use? I was a bit confused when I started looking at the Chevy parts on Summit. They didn't list a 200R4 mount, but just about every other one.