FP specs:

Normal Run 3.2-3.6 bar
With vac line to pressure regulator disconnected 3.7-4.2 bar
After 1/2 hour stand/off No less than 2.5 bar
[Bar = 14.5psi]

The fitting is on the fuel rail and is the same thread as R12 fittings. Don't know what your GM uses.
Pevious OVP info post is correct.