You have to follow the top hose from the radiator to the engine. The hose connection at the engine most always has a housing for the thermostat. So - remove the bolts there of that housing and replace the thermo. or in your case intall one.
Check or better , change the thermostat.
Yes
( 20.0 U.S. gallons ) according to my Chilton's book for a 1989 Ford Crown Victoria
get a 195 degrees one, i got mine from o'reily's for 8$ and never had problems with overheating
Yes, they are identical
On a 1989 Ford Crown Victoria : ( there are 5 lugs per wheel , total of 20 )
C-4 aod
147 hp
About two tons.
According to my Chilton's Auto Repair Manual : A 1989 Ford Crown Victoria has a ( 20.0 U.S. gallon gas tank )
http://www.modifiedlife.com/1989-ford-crown-victoria-car-radio-wiring-schematic/ any car audio web page will have diagrams
it is 215/70/15