Ripley: I concede your point re: track width, I misread my references, though cromwell also used the 15.5in track. The track width I dont see as a problem for a dual kit though, at this scale, the 2.5inch difference (assuming cromwell mark with 15.5 inch track) amounts to just 1.1mm each side, the 8inch length difference (according to my sources) is less than 4mm difference, representable with a new overlayed rear hull plate.
Regarding the suspension however, British tanks have never, to my knowledge, used torsion bars owing to maintenence problems (though some light armoured vehicles, such as APC's do). Comet I believe was the last of the British tanks to use Cristie suspension as on all cruiser tanks from the A13 onwards, I would be interested to know what source you have that states that Comet used Torsion bars.