I wont mention that I would think very long and hard before cutting into such an original car...Whoops, I did so, didnt I?
Anyway, when I got my wife our one new Cadillac in 1995, it had a roof, and we seldom used it.
Also, as a Past President (we judge original cars at the GN), I would love to help judge your car as it is, and maybe award a 1st place trophy on it at a Grand National, which would be almost impossible to do after being altered with an aftermarket accessory roof, new headliner, etc, etc, etc. Once you alter a nice original car, sadly, it is no longer that, no matter how nice it may remain and how professionally the job was done.