Has anyone here done this?

I am considering the acquisition of a C175a with a runout engine
and replacing the engine with an O-300 engine. Is there a kit for
doing this?

Does the engine mount have to be replaced? I am guessing
the airframe is just a C172 airframe. Am I wrong? Does the
cowling have to be replaced? I assume the prop has to be
replaced (I would not want to have the prop repitched; I
don't like the idea of cold-twisting prop-type aluminum).

It is my understanding that the GO-300 engine TBO is 1200
hours, because of its higher RPMs; is that correct?