without seeing them, i will go out on a limb [with a saw of course ! ] and say 70's to 81-2, maybe even 83, would be DC items.
of course knowing what diode number[s] was/were used on the original chrome boxes would be a big help in identifying the boxes you have.

all the chrome DC boxes i have owned have an ink stamp below the female plug that shows the part #, and has a sticker on the plug's long side saying "electronic h. e. ignition" along with the pentastar and chrysler corporation.
the one in my hand this instant has an ink stamp of 4120534, underneath that, 2299, and then what appears to be a smeared pentastar.
the diode thing has the numbers 3597625, and underneath that, A7926
this box was from 1978 or 79. it was used with one of those huge accel super coils, but i don't remember what ballast resistor value was used with this setup.
hope this helps somehow.