Torque Strap?

First, put it on a frame machine & get things square again. Next. I'd break down & use a motor & mid-plate. Sorry but your car is obviously beyond the point of "stock appearing" so you may as well add what's necessary. This will stiffen things up but retain something of a "stock" appearance. My car is similar but I added a full cage including snout bars running outside the inner fender panels to retain a stock engine bay appearance.