Neg cable end, as well as return spring bracket and intake surface were bare metal prior to painting engine to provide good ground and gets sandwiched between the two. AVS2 is only used for cruising/local shows, but the original restored 4429S is basically identical.
Try to find a spring with a minimal amount of tension at rest. Also, there should be a washer between the clip on the throttle pin and slotted kickdown arm, and the throttle return spring should be hooked on the pin inside the U shaped end of the throttle cable. Proper throttle pressure...
This is the key part that you stated. Once the pump is spinning and circulating fluid through the circuits you are at the proper level. Under no pressure gravity takes over.
Edit: I always start and warm up the car in neutral.
I contacted Melling a few years ago, and they told me that the standard pump was made to have a standard pressure of about 45-50 psi. Luckily with the big blocks that can easily be changed with the external spring replacement or shimming.