most likely a sending unit problem
It is behind the distributor at the firewall.
The 305 can actually run and drive on a low as 5psi of oil pressure anything lower you're in trouble. A 305 should typically have anywhere from 40 to 15psi to be in excellent running condition.
Fuel Pressure Regulator is located on the fuel rail.
To remove the heads on a 305 Chevy, first disconnect the battery, carb and throttle cables. Also disconnect the sensors and vacuum hoses. Unplug water temp gauge sensor on the thermostat and disconnect pump from brackets.
If the Buick 305 is really a Chevy 305, then the motor mounts will interchange with a Chevy 350.
1350-1450 @800rpms
A tan/white wire goes from the sending unit to the fuel gauge typically on a (example) 1985 Chevrolet Silverado 305 tbi.
Oldsmobile used Chevy 305's. 76 350 rocket 77 305 Chevy
There is no information on the internet about what the special feature of the Chevy 305 engine is, in fact, the Chevy 305 and 350 are interchangeable, one is just an older model.
305 horsepower
On the drivers side of the block, right above the oil filter.
YES they are the same.