As you may or may not know this is a tremendous task
. Convertibles have added torque boxes for rigidity. If you were to cut the top off a classic it would be a matter of time before the car would start sagging or even bend like a taco. I would say making a non convertible car a convertible is much more difficult than making a coupe a fastback. And we all know what an undertaking that can be. Besides ruining the classic value of the car, the resale value would be much lower. Just my
.02 cents.