Torque Boxes vs. Frame Connectors

Stick your head underneath your coffee table. Those triangle shaped pieces of wood in the corners are torque boxes. You can see how little it takes to dramatically increase the rigidity of the frame.

Regarding the frame connectors, I actually have no knowledge of what forward thrust is. But what I was taught they do, is prevent the up and down stresses on the middle of the unibody. Picture a car doing a wheelstand and you can easliy imagine how much the floor pans want to bend in that space between the front of the leaf spring mount and the transmission crossmember. If the car is trying bend into a hump, it's also putting a lot of extra stresses on the U-joints and tranny tailshaft. Probably led to to more than one tailshaft bushing failure over the years.

While the typical square tubing welded only on the front and back go a long way towards the goal, the extra time and money you spend on a fitted set that get welded to the floor pan as well are FAR superior and a no brainer assuming you've got the extra cash.

IMHO the best you can find are made by John Paseman at US Car Tool. http://uscartool.com/documentation/67-75-a-body-frame-connector-install-pics/