nucleus wrote:

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?

I have heard of replacing the GO with a Lycoming O-360 or a Franklin, but I'm not sure about the O-300.
I'm pretty sure the cowling would have to be modified or replaced. The 175 has a hump on the upper
cowl with the prop hub/spinner aligned at a higher position due to the gearbox. That would have to
change with a different engine. You would need approval data, so you need to find a STC for the mod
you're interested in. There's lots of good information at the Cessna Pilots Association,
http://www.cessna.org. They may be able to help.

Mike