Don't panic!
The 440 and 426 cars also had stronger suspension. Did your 383 car get that too?
If the sump on your engine sticks slightly below the k-frame it might be a good idea to weld a plate onto the frame to protect the leading edge of the sump. But you don't
need it as such.
Same with the re-enforcement of the torque boxes at the four corners of the floor secton. You don't need them but if you race the car at all (remember a lot of 440 and 426 cars were intened to be street/strip) you should add these to your car. They are a good idea anyway because they stiffen the chassis slightly.
If you want an even stiffer chassis (a good thing) or if you race a lot OR if you use slicks AT ALL you will also need frame connectors welded in.