I ordered the service manuals on CD off of eBay -
Chassis service manual 81-270-3250
Body service manual 81-270-3260
Published by Dave Graham, Auto Literature inc. for
Challenger, Dart, Charger, Coronet, Polara and Monaco
Mine is a 73, but I'm sure you can find the 72 (or it may even be the same)
It's Authentic Restoration stamped. Really just two PDF's one of each original service manual. I looked on eBay and couldn't find it again. But I'm sure with some searches on the above you can find what your looking for