Your gearbox choices are jc5 089 which is a ph1 speedo drive gearbox with a different final drive. Jc5 129 is also a speedo drive gearbox and is found in ph2 172's and cups. Some have the speedo drive sensor fitted and some don't. It also has a different final drive to the 089.So I can put any 172 engine into my 172 cup, and as long as the gearbox has a speed sensor (like my existing one does) it'll work fine
Will a later 182 engine fit and work?
Are there any other gearboxes that are compatible?