Well, I learned a little bit more about the car today. I disconnected the vacuum line to the fuel pressure regulator and installed a vacuum gauge to measure the sourse vacuum. I then connected a vacuum pump to the regulator itself.
I measured 20 in.hg. of vacuum at the vacuum line to the regulator, at idle. Opening the throttle caused a momentary drop in vacuum, which quickly stablized back to 20 in.hg. I would expect that lower manifold vacuum measurements with the car driving down the road and under load.
With 0 vacuum on the regulator, I measured 60 psi fuel pressure at the fuel rail. When I drew a 10 in.hg vacuum on the regulator, I measured 55 psi at the fuel rail. When I increased the vacuum on the regulator to 20 in.hg. (same as the manifold sourse), I measured 50 psi at the fuel rail. It appears that maximum fuel pressure on the rail is 60 psi and the pressure drops 1 psi for every 1 in.hg. of vacuum applied to the fuel pressure regulator.
Does anyone out there know whether or not these measurements are normal for this set up. My Haynes manual is deficient in this regard. Any help here would be appreciated.