Oil Pressure in Early Cars

I've been wondering: what is an expected oil pressure range in a 911T through the rev. range?
I've driven a couple of '70 911T's in the last few days. The first car felt fairly lethargic above ~3500rpm (not very willing to accelerate) & I noticed that the gauge stopped climbing as the revs rose (the highest pressure reading was maybe halfway up the gauge). As the car was in a fairly poor state of tune (ignition components & valve adjustments had been forgotten for awhile) I wasn't sure if this could be the cause, or if low compression would be the culprit.

The second car felt v. peppy in comparison, but surprisingly the oil pressure gauge exhibited pretty much the same characteristics.

Is this normal for these cars? I would have thought that the oil pressure should continue to rise with the revs untill redline?

thanks,
Andrew