I picked up the old '84 and it needed a ton of work. now its running and driving, minus a power steering pump and belt.
was going to park it one day after pulling it out of the shop and the cables snapped. The holder/ connector for both rears to the lever is now MIA. I'd like to get all new cables but cant find the metal connector that joins all three cables or the adjuster to take the slack out.
The car is an '84 Z28. im not too sure of the proper names of the parts im looking for as ive never had to replace it on any vehicle ive owned or any customers car before.

 

It's Called An Equalizer, It Shows As Still Being Available From GM

1984 Chevrolet Camaro Base 2DR Equalizer. Parking brake cable. Equalizer, park brk cbl - 14065766 | Wholesale GM Parts Online, Louisville KY

 

The piece you are looking for I believe is called "equalizer".

I don't think it's unique to these cars. Probably any GM car of similar age would have the same one.

Last time I checked the cables themselves were mostly still available. Might want to check rockauto.com, they seem to have the most complete collection of such things available.