I have a JA12 body in very good condition, its from a coil spring samurai. I am wondering if it"s possible to replace my old worn out SJ body with it.  The SJ is a leaf spring chassis/frame.

Is it possible or would there be problems.

It should be possible, the body panels look to be the same.  Might be a slight difference with the inner fender well.

Body swaps between years can be a pain though.  Sometimes there is a lot of electrical that has changed that isn't documented particularly well.  You might be better off putting your drivetrain into the coil spring SJ.

Was thinking about the drivetrain instead but wasn't sure.