There should be a lever in front of the radiator, towards the center. You may be able to reach up from underneath and move it to pop the hood. Since you said the handle is loose it sounds like the cable broke. Also try popping it with your hand incase it is stuck open, but stuck in place.
Good luck. I once ripped the grill out of a 78 volare with my bare hands over a stuck hood, and bad ignition relay. Not the best access for sure.
THere are some pics of the open hood on a 5th ave on Ebay that should help you identify what your after. It will be a short bar with some bicycle cable hooked to it. (at least my experience with older mopars says it should be.)