Fuel pressure sender recomendation

Go with the MGL recommendation. Best chance of giving meaningful readings. Best chance of sensor being compatible with EMS-1.  Problems? you got, it take it up with MGL.

7.26 psi is the MAX pressure.
Nominal Operating Pressures will be closer to 6 down to 5.
The Sender outputs 0.5 to 4.5 volts for pressures from 0 to 7 psi.
There is no reason it could not put out 5 volts at 7.8 psi.
It is just that UMA is not going to guarantee it or that the curve will still be linear when out of the spec'd range.
Set your Redline Alarm at 6.95 psi and it will get your attention that something is wrong,

Fuel pressures are determined by a spring in the Fuel Pump.
They tend to fail by getting weaker or flat-out breaking, resulting in LOW Fuel pressure.
Even more common is the Fuel Pump Diaphragm tears and pressure drops to near Zero.
Overly High Fuel Pressures do not tend to be a problem.