'56 to '62 were available in soft top only, both tops, or hard top only. Hard top only is rather rare but they are seen from time to time. I used to cruise the streets years ago in a hard top only '57 fuel injection. A convertible top can be installed in a hard top only by installing all of the soft top hardware and the latches on the rear deck lid. The deck lid latches would be the hardest part to install as all the mounting holes are already there for everything else. You would need to make an exact template off of another lid to be sure to get them in absolutely the correct position. It might be easier to just buy a used deck lit for a 2 top car.
Tom