Yes, they are identical
For a 1991 Ford Crown Victoria : " regular " unleaded , 87 octane
In the gas tank.
4
Yes, both model years are AOD transmissions.
According to my Chilton's book : For a 1991 Ford Crown Victoria ( 5.0 / 302 and 5.8 / 351 ) With engine oil filter change ( 5.0 U.S. quarts )
10 degrees advance
Often in the owners manual is where i found the one for my 1991 Crown vic. Hope you have your manual?
The best is to buy a new one.
On a 1991 Ford Crown Victoria : Using a funnel , you add automatic transmission fluid through the ATF fluid level dipstick ( in the engine compartment , near the firewall , on the passenger side of the engine )
In a 1991 Ford LTD Crown Victoria ( 5.0 / 302 and 5.8 / 351 ) Follow the top radiator hose from the radiator , it connects to a housing on the front of the intake manifold . The engine cooling thermostat is inside the housing
oN THE 91 FORD CROWN VICTORIA YOU WILL LOCATE THE SPEED SENSOR ON THE DRIVERS SIDE OF THE TRANSMISSION ON THE TAIL SHAFT.
Probably computer controlled and not adjustable