I have a 73 Barracuda with all numbers matching running gear. It has been a driver since I bought it in 2000. I have been working on it periodically since while thoroughly enjoying and collecting KUDO's on it over the years. Everything works great, even the OEM A/C. It is now time for it first big upgrade, a BIG BLOCK. Since it is not a low production vehicle I want to put a 440 in it. The only thing I have done to the chassis since owning the car is rebuilding the rear springs and install bolt on sub-frame connectors. On the sub-frame connectors I made a U bracket and welded it to the front of the frame connector so it would wrap around the torsion bar cross member encapsulating it. I then bolted that through the cross member and up through the floor with a plate on the interior floor board to capture and clamp everything tightly together. I bolt the rear through where they attach at the rear sub-frame as the manufacturer designed. But I did one addition reinforcement point and that was where I welded a plate onto the connect bar that aligned with the rear seat floorboard and did the same clamping method there as I did at the front. The difference with the car after sub-frame connection was like night and day. This mod has worked really well for me. Now to my question: Did E bodies that had big blocks installed in them from the factory have any reinforcement in the chassis such as Core Support braces, Inner Fender braces, Front Torque boxes or Rear Torque boxes? If not, since the 440 build plan is to keep it mild, would this be necessary or recommended? I don't want to do this for the sake of doing it but would if highly recommended. Thanks in advance for your input and advice.

IMO If I had to take it to the next level for the big block I'd at least add the rear torque boxes..You've got the twisting aspect of the equation taken care of now it's time to make sure the torque generated from the big block doesn't pull on the front spring mounts...They were there from the factory for a reason...
Is it an absolute necessity ?? Possibly not..But you've already done the hard modification the rear torque boxes would be an easy addition and good piece of mind eliminating a potential problem ...

Thanks for your reply. You have an excellent point. I thought I may do the torque boxes and the core support braces. I just was wanting to know how much the factory did for the big block cars versus the small block ones. Mine engines is the 318, still taking a lickin and keeps on tickin. But now I want more.

The front and rear torque boxes were used in different applications...Small and big block...I could tell you "the torque boxes were used in XXX applications" but there seems to be many exceptions on their use with or without them...The rears seem to be much more common than the fronts..I'm not aware of any factory core support bracing from the factory but the aftermarket seems to see a need for it..And lastly don't forget about considering the K frame skidplate if you're using the factory 6qt oil pan..

It really comes down to what you intend to do with the car..Even a "mild" 440 by today's standards is still more HP than the factory offered back then..If you're just cruising around you probably don't need any more than you have..But if you like occasional road blasts then adding some performance/safety enhancements is a good thing...