how much would i benefit from having a Lower Core support frame brace and inner fender braces. im going to do Frame Connectors, a complete set of front & rear Torque Boxes so i dont twist the body. this will be on a 72 demon.
It makes a significant and worthwhile difference. It helps reduce cowl shake on rougher roads and solidifies the connection of the front clip of the car to the passenger compartment. It is well worth the effort to weld the front shock towers solidly to the inner fender wells and box in you steering mount and weld up the seams on the K-frame and torsion bar crossmember while you are at it too.
The combination of all of the above makes a night and day difference in improving the overall chassis rigidity compared to just doing the sub-frame connectors and torque boxes, which are number one in priority.
A Monte Carlo Brace added to the engine compartment makes a noticeable difference as well.