Yes it is!
go to the Toyota store n ask them if they don't no go on Google and type in this how toinstall rear speakers on a 1991Toyota 4runner
it mounted on the throttle body
Typically, yes. Most 1990-1995 4runner's came with the same factory 3.0 V6 engine and are interchangeable.
Fuse block in engine compartment right side.
look on the intake manifold it will be stampes into the manifold cast.
Freon but you can convert over to the new stuff
By your left foot about 8 inchs up on driver side floor board
The thermostat on a 1991 Toyota 4Runner is located on the engine block. It can be found by following the large hose coming from the radiator.
dexron atf is what Toyota recommends, ive used it a hundred times its fine