Rust is pretty much always more extensive than you originally thought, so you should definitely get an in depth idea of what the damage really is and then plan on replacing even more than that.
Patches can actually be more labor and time intensive than replacing an entire panel, there’s definitely a crossover point. Because the OE panels are all spot welded, it can be significantly less welding to install an entire panel than a large patch that has to be welded completely along its full length. Obviously there are other considerations, but I think most of us tend to underestimate how much work a few large-ish patches can be.
I know I did multiple patches to repair the floor of my Challenger, and after all was said and done it would likely have been faster to replace the whole pan as a unit. Not to mention a cleaner looking finished product. Materials wise it was cheaper than buying a full pan, but by hours of labor I definitely lost.
For the rockers, remember those are very structural, and you’re going to want to set everything up level and square before you take the old ones off so you can check that everything is level and square as you install the new ones!
