Found an original CA registration renewal card in the paperwork dating back to '79. The silver one was originally titled to the parents of the brother and sister who drove it.
Oil change many years ago.
Mechanic used old label maker to keep records of his work. Also has a label with the owners name on the door jam. The firewall is cracked on the other vehicle. This one seems solid.
Cracked firewall is a common problem which is a result of excess brake leverage. Send Fossil or one of the other vendors a PM and order a brake brace. It will prevent cracking on the uncracked car. Stan's (fossil) is the original and a well engineered and simply installed safety and reliability upgrade. Money well spent.
67.5 SRL311 #00050 - Silver - SU
67.5 SRL311 #00544 - Sora Blue SU
68 Roadster Race Car
69 SRL311
69 SRL311
72 PL510
74 260Z - Silver
Both are single master cyl units. I'm certain my other roadster has a crack. When I push the brake I can see the firewall flex and a crack is visible. The roadster in this photograph above has no flex and I see no crack. Thanks for the tip about the brace.
I've seen cracking in early firewalls, but it is less common than the later cars. There have been some creative solutions, but I don't have photos or links to them.
I finally have a plan. The silver car is original and has far less rust but for some reason the dash was rusted through at the bottom. It also has the wrong year ds fender. I'm going to pull all the best parts off the gold one including the black interior and make a complete original car and just maintain it as it. In the process I'm stripping just interior and trim on the gold one, weld in a few patches and paint.
I have completed swapping the dash and moving all the best parts to the good dash. The other dash needs sand blast and patching because it rusted through. Here I'm getting ready to install it.
Put the other dash in, fixed up the trunk and body work to the left rear. Mostly just weekend driving my son around town to get groceries for the family. Every trip someone looks and smiles.