I thought it might have been a different tiller as the way it was described ,sounds like it's had a replacement engine fitted because the Rover mower/ tillers were from the sixties and seventies and the sprint motor being from a different decade.
The ripper you've mentioned is a depth tool bar,shouldn't be too difficult to make the missing parts just time consuming. To me it looks like where I circled the part in blue in the pic below it would be made from spring steel (the short steel bit with 3 holes ,1 hole where it locks in and 2 holes where it bolts to the spring plate 26 )you could make this part from an old car stabilizer bar but it will take a long time drilling the holes at home without special hardened drills.I've drilled spring steel with Sutton drills and you have to start with a small drill and slowly go up in sizes and keep sharpening the bits as you go.
Video showing depth bar adjustment below.
Old Tillers restored look great for display purposes but if you wanted a small tiller to use new ones are cheap to buy.
