Unless things have changed since '92, the front bumper is bolted on at 4 points. The top two attachment points are part of the snubbers that hold the grill in position with the hood closed. The bottom two attachment points are accessed through the tow hook covers. (Don't forget to detach the outside air temp probe that's part of the driver's side cover) Then the bumper pulls straight off.

For the rear bumper, there are some "expanding rivets" (AllData phrase) below each rear lamp assembly (seems a bit high up to me). Instructions say to open the cover on the lamps inside the trunk and the rivet is visible there. The other rivets (based on the lousy diagram) appear to be on the floor of the trunk where the rear bulkhead (the part of the car that holds the lamps, trunk latch, etc.) threshhold meets.

If the car has an antenna inside the rear bumper (later models, I think), there's a disconnect point that appears to also be on the rear bulkhead of the trunk - disconnect the aerial lead there and push the grommet through from the inside to the outside.

Once these attachment points are released, the rear bumper pulls straight off as well.

Again, this is for a '92 140 chassis - don't know if everything is the same for a later model.

Good luck.