Ask the Editors: Honda Big Red Frames
The difference between the 1982 and 1983 model year frames would have been negligible but going from 82 to 84 will pose a few changes to account for the addition of the shaft drive and an increased towing capacity (up to 700-pounds).
That being said the frame wasn’t entirely new but different enough to where Honda assigned a different part # run for their production cycles (JH3TB051XC133783~ for 1982 and JH3TB0554EC300001~ for 1984). Judging by the OEM schematics, some welding/ reconfiguring would be necessary for the change in drivetrain but rebuilding an entire frame wouldn’t be necessary (particularly if you’re trying to mount the earlier 82 engine into the slightly more accommodating 84 frame).
Finally, yes the 84 shaft-drives were indeed differential-equipped.
Your best bet at studying the differences would be to consult the service manuals. Believe it or not, 3WheelerWorld has actually made available most of the service manuals as free PDFs here.
