I did some more digging around and learned that there were indeed 2005 model year Dodge Magnums, and found the owner's manual for the 2005 model year online at http://www.dodge.com/en/owners/manuals/ (you have to toggle the model year and model name to load the .pdf file version of the owner's manual). The '05 Magnum's manual indicates all three rear seating positions have lower LATCH anchors to accommodate LATCH installations, but it also states not to install 2 carseats side by side using LATCH and to use seatbelts for side by side installations. Here's the pertinent blurb from page 52 of the .pdf file:
All three rear seating positions have lower anchorages
that are capable of accommodating LATCH-compatible
child seats. You should NEVER install LATCH compatible
child seats such that two seats share a common
lower anchorage. If installing child seats in adjacent
rear-seating positions or if your child restraints are not
LATCH-compatible, install the restraints using the vehicle’s
seat belts.