...to make the running gear for the Comet available separately or better still make a 'downgrade' kit to convert to a Cromwell.
For such a Kit you'd need to make the idler slightly smaller, the road wheels slightly narrower, the track links different and slightly smaller, the front and rear deck plates would need to change and a new Turret and 75mm gun added. Also depending on which Type you went for (a Mk IV Type d would be more common for Normandy) you'd most likely want to take away the side-escape hatch on the drivers side. But this can be patched and won't be seen because it will be covered by an extra tool box on that side.You'd also need to change the rear plate as the fish tail exhausts would not be needed.
Doesn't sound like a great deal does it, LOL! If you're interested let me know as I have all the information at my fingertips. I've ate, slept and poo-ed Cromwells for a coupled of years now...hence the interest in the Comet...which I might add compares well with my own endeavours in the Cromwell arena.