It's not likely that you have a Ford 300 I6 in your Jeep, because that motor is longer than the AMC 258 I6. Plus, the tranny fitment would be a problem. Anyone wanting more cubes than the 258 typically installs a small block AMC or Chevy V8, which are actually shorter.

It's much more likely that a PO swapped out the 258 carb for one from a Ford 300. that's relatiely easy to do.

1977 CJ-7, fiberglass body, AMC 360 w/ headers, DUI ignition, Edelbrock intake and Holley 4150 carb, TF999, Dana 300, 4.56 gears lockers, York air comp, 4" susp lift, 2" body lift, BFG 35" M-T tires, Megashifter, AGR pump & box, REP8000 winch.