OK here is where I am at so far:
Per Allan I have removed two screws at each location marked by a green arrow; total of four screws, two each side. There are also two screws close to engine centerline at the location marked by the red arrow, but removing them did not seem to do anything. I have a hunch that they are for mounting the can motor to the frame, judging from the parts layout on Lionel's site.
Next:
Again per Allan, in this view I removed two screws at the location marked by the green arrow; one each side of the rear power truck steam chests, as suggested.
Lastly:
Per Alex M. I removed two screws at the location marked by the green arrow near the front; one each side. With these screws removed the front of the frame lifts from the upper boiler by about 3/8" easily. Not related, but the red arrow looks like a screw is missing from this location, but I have no idea what it might have been; there are threads evident in the hole??
Now when I place the engine on the bench wheels down and try lifting the back of the cab as suggested by several people, it will not lift off the frame. It is stuck fast, and fairly aggressive effort will not budge it.
Anyone got any ideas what I am missing here? I am at a complete loss.
Rod