On Friday, April 21, 2017 at 4:11:21 AM UTC-4, wrote:
Converting the early 150 model to 180 hp is now available through Mike Horton of Lubbock, Texas. The STC allows for the o320 to be replace with the o360 A1A. The late Jeff Cloud had the arrangement in his tow plane and it was very good. No it is not a 235, nor should it be, but it is a very adequate tow plane. I believe that very Pawnee is still towing in Mass or somewhere up that way.
Mike Horton has assumed the ownership of the STC that is in his late fathers estate. The engine mount is from the Piper Commanche 180. I have spoken with Mike and he has a tremendous amount of information on the conversion.

Mike is available at 806-781-3641, good guy with tons of information. I have a Pawnee 180 that does a fine job of towing. If you are not running a commercial operation and looking for an efficient way to tow you should consdider the Pawnee 180 option. It is certainly much less expensive to operate and the weight difference between the 235 model Pawnee and the original 150 model was over 400 pounds. If the FAA would allow the field approval for the new 390 engine it would make a huge difference in the airplane. My 180 Pawnee toes better that the 180 super cub that we used for years. I think our facebook page for Treasure Coast Soaring shows the 180 Pawnee that we named, Yellow Gorilla. Bob