When the fuse block is found (seems like it screws-down from its "hiding place"?), each of the fuses should be labelled as to what they are and their amp rating.
Clock and cig lighter will both be "direct feeds", which means they are on all of the time, not "switched", which are on only when the ign switch is "on". The power antenna is probably switched, as it is only needed when the radio is on, I suspect.
Power antenna mechanisms can fail on their own, though, so making sure that fuse has not failed is important and then that the antenna mechanism gets voltage to operate. In many cases, the power to the unit is fine, just that the mast's internal items have separated.
The heating elements in the cig lighter can fail with use, by observation. Getting clogged with tobacco, for example, from lighting many smokes. If that cig lighter is used as a power source for some other devices, it might well be that the electrical interface in the housing does not match-up with the item being inserted into it. I discovered that there can be a difference between a "cigarette lighter" and a "Power port" . . . both look the same but take a different plug-in plug.
Electric clocks, the non-quartz movement versions, can just stop working with age. Usually, the combination of internal oil getting gummy and the contact points getting corroded with time. Similar to ignition contact points, cleaning them can make them operational again. Plus some new light oil for the mechanism. NOT "transistorized" or "electronic" like later versions were.
I wanted to mention these things to ensure you were aware of them, for good measure. No more, no less.
Find the fuse block and get it down to where you can look at the fuses. Sometimes, the old glass fuses might look good, but could have issues in their ends (which could not be seen internally). A simple test light could indicate if they are good. As mentioned, each should be labeled as to function and amperage.
As the 1978 C-body began life in the 1974 model year, you might find some information at
www.mymopar.com in the Chrysler MasterTech downloads and also possibly at
www.hamtramck-historical.com, with their "Library" section for 1974 Chrysler vehicles, in the "Data Book/Order Guides" sections. In the MasterTech segments, look for "New for 1974" titles.
Take care,
CBODY67
