I believe all convertibles got them in the front and rear since removal of the roof weakens the crap out of an already weak unibody.
As far as them being in the front on hardtop cars with big blocks , and 4 speeds of that i am unsure. The us car tool torqueboxes are not repops, that is exact copies of the factory stampings. They are bent from 1/8" plate steel . Very beefy, however they dont fit as well as i would like.
I made my own templates out of cardstock similar to the us car tool ones and bent and installed my own.
If your looking for more of a stock restored look i have seen torque box stampings that are shaped as originals. They are not 1/8" plate so are prob not as strong as the car tool ones, but prob fit better and are perfect for a restoration where the originals are rotted beyond using.
Matt