Frame? You mean the frame you gotta add, yourself, right?
You basically plop your avenger shell on a standalone frame. There's nowhere in the rear for suspension -chassis mounts with the beef for a drive axle and there's very little structure in the back half. Traction and a loose converter would twist that car right up if it wasn't significantly reinforced.
Remember, all late model fwd basically have the rear half of the car there to keep it from dragging it's *** on the pavement. The back half is just along for the ride, so there is no incentive to add a lot of structure to it.