Replacing Trucks on a Lima N Scale Caboose

I have a cheap Lima N Scale Caboose that was given to me. I fixed it up a bit and I’d like to replace the stock trucks and Rapido couplers with Atlas trucks and couplers. However, the stock trucks are not held on with kignpins or screws. Rather, the truck bolster has a bifurcated post with a flange on top that pops into a hole on the chassis. What do you guys suggest?

If you can get the body off, remove the trucks from the frame and fill the hole in the car bolster. You could use epoxy or glue in some plastic bits. You could even super glue a wood plug in it. When the filler is dry, drill a hole in it so you can mount the new trucks with a screw. You may have to tap the hole. (Make threads in the hole)

Cement a short piece od Evergreen styrene tube in the hole, then attach the replacement truck with a screw.