This item can be modified to fit a Hornby Class 20 (X9841)
The bogie cover and wheel fit straight in with no modifications needed.
The basic problem with converting this to fit is the how the pickups are connected. If you look at the main photo above you can see the pickups are held on by nuts, these get in the way and need to be removed.
In the one I did below we simply glued the pickups to the drive units body and when the glue was dry we removed the nuts and cut off the bolts that were sticking out. The drive unit then fitted fine.