They are not that high , that engine has a lots of hour , they are all running around 290, #2 and #3 are the lowest and yet they are the one running best....Did you test all 4 cylinders ?
They gotta have pretty much the same in all ofem. 25 psi difference and no more.
Cranking with the starter ----> 400 psi for a motor in decent condition.
480 while it is running.
Springs are available. It takes a lot of time searching for them tho.