This STC is to install a Lycoming O-320 150/160 hp engine. There are no airframe modifications required with this STC, you are changing the firewall forward to be like a PA-22-150.
Only conical engine options are approved PA-20 and PA-22. Below is a list of the approved engine options:
Conical : A1A, A1B, A2A, A2B, A2C, B1A, B1B, B2A, B2B, B2C, C1A, C1B, C2A, C2B, C2C
Any other O-320 series engine that is converted to one of the above models in accordance with Lycoming instructions is able to be used with this STC.
The propellers that are approved to be used with this STC are the Sensenich M74DM, 74DM6, or the McCauley 1A175GM propellers.
This STC is valid on all models of the PA-20 and PA-22.