Welcome to AF Stingervf
It's a different bell housing, which is permantly mounted on the transmission.
However there should be lots of good used transmissions for your car with the right bell housing. Stick to the same model transmission and the swap is a snap.
Grab the 289 motor mounts from a wrecked car. I can probably look up an address for everything that you need if you need it.
Personally I would use a 302 motor. They are the same block and heads as the 289.
It's probably easier to send me a private message with any questions about your car.
I've owned a pickup built in the same era so I probably know more about them than most people on here. However I'm rarely on the Mercury sight.