Here is the jack data from our 68 LOS 04D:
Square, 8D on the mast.
Base - blank.
Load Rest - CAMARO 1968

I can e-mail photos if you'd like.

There is someone on CRG with a pair of NOS phone receiver 67 Conv quarters.

Granted not the original one to my 12D of 67 (68) LOS Z but it is correct for LOS cars as it came from one and has the correct date code. I also look forward to reviewing this Legends manual and would offer up reviewing the 68 section if you are wanting input but that is strictly up to you as I am sure you have several folks that are much more knowledgeable about them than I am but wanted to offer my input if its accepted.