How about these?
From their website:
They are laser cut to precisely follow the floorpan contour.
Laser cut from 11 Gauge steel (original factory rails are made from 14 gauge material) and CNC bent for a precision fit, these frame rail connectors are designed to be welded in to your existing unibody floor pan. No cutting of the floorpan is required and once welded in, they create a fully boxed frame rail connector that is stronger than the original factory frame rails!!
These are designed to follow the contour of the original floorpan and be welded directly to the original floorpan for maximum strength.
These frame connectors also have additional internal bracing to provide additional strength in the critical rear floor pan area.
70-74 Dodge E-Body (Challenger) includes convertibles and hemi torque box cars $189 pair
70-74 Plymouth E-Body (Cuda) includes convertibles and hemi torque box cars$ 189 pair
http://www.uscartool.com/Bframeconn/index.htmlI'm considering a purchase here.