I don't know what the upper limit is that you are likely to reach. Normally, guages are usually designed with there being plenty of room above the likely maximum value. Now, I just bought an NOS oil pressure guage and it has a little tube affair that disorts with the pressure and rotates the dial against a spring.I suppose that the spring could fail or change characteristics to give you higher readings.
The 216 has a small oil puimp that feeds the mains, cam bearings, rocker arms and fills the dipper troughs. The oil pump itself has a relief valve that opens at, I think 60 lbs. Also, there is a small plate on the driver's side of the block that contains the oil distributor valve. If that valve stuck closed, it would stop delivery to the rocker arm and the rod supply nozzles. That might cause the higher pressure and that problem would be vey bad for the motor.
