can anyone tell me the required fuel psi on a 77 280z???

It should be between 35-40 psi when running (that's where mine sits at). The FSM states 36.3 psi at the manifold exactly.

do u know where the best way to test it is at? i taped int tje line right after the fuel filter just because i dident see any other place that would be easy, i havent tried it yet tho i guess my battery is dead so i gota wait for it to charge up

After the fuel filter, before the fuel rail, is the right spot. Pull the small wire from the starter, and turn the key to Start to run the fuel pump, after you've charged the battery.

36.3 psi = 250 kPa so precision isn't a big deal here...

ok im pretty sure when i checked it there was about 39 psi any other reasons why the car wont stay running?