Some good progress tonight.
An expert called in to advise on cage according to the Blue Book, confirmed what we had in mind really.
Feet cut off the front part of the cage ready to shorten the legs to fit onto the spreader plates.
Floor plan cleaned of about 80% of its wax stuff, rear corners scurfed up ready to weld the spreader plates in when we're happy with exact position of cage.
Door bar brackets removed from front part of cage to be welded on at a more appropriate height (and even both sides

).
Gearbox removed from engine and brought back to the works bench that is my dining table for surgery, loom also brought back ready to be hacked down as far as it needs to be.
Thank you Mr DH, real sense of direction after tonight, certainly moving on in the right manner!