I took the booster off and shook that little rubber disk out of there. I glued it to the back of the booster with 2-part epoxy and then put it all back together. Now the car stops as great as you would expect a 40 year old Datsun to stop with factory brakes!
Another day went by and the car still runs. amazing. The suspension is very sloppy. When you get on the throttle, the car squats and wiggles at the same time. It kind of feels like driving on air bags.
I tested power near the fuel pump and it shows power. I decided to just swap out the pump. I had a new pump that I put in to the 280ZX turbo so I pulled that one out, put it in the 280Z, and it started up.
I replaced the larger fuel line from the tank to pump (3/8) I also cut the wires back a bit so the pump has all new wires leading into the car and then connects to the factory harness under the seat.
Last I checked the brakes were still giving lots of pedal travel before applying pressure. I've got some glue to fix the reaction disc. If the disc is in place then it was not the cause of these issues. I'll try adjusting the length of the plunger. I also have a 1981 280ZX booster I can pull and install as I've read about that as a brake booster upgrade.
Pictured here is the R200 LSD I found recently and the coilovers pulled from the rear of a 300ZX. I left the shocks and just bought the springs, threaded sleeves, and top hats.