I dont know why they are not recommended. I do know that Fox verts came with additional bracing from the factory. I believe that included some plates that fit between the inner rocker and the torque box area, and a triangular brace at the front. At one time Ford Motorsports sold these items as a kit and I installed it on my 79 Capri. I think I had to remove the plates to later install weld on subframe connectors.
Read the install directions, then crawl under your car and look. No doubt it can be done, may just take some finagling.
