I dont know a lot about the model 80 but It would be the other option for what you may have if your tractor looks like mine.
Im pretty sure the 80 did not have a spark lever. So if you have a spark and throttle lever together you probably have an 18-27. Some where along the way the governor was changed. I have included a picture of a governor off an 80 and you can see mine in the picture I sent before. You cant really go by the magneto, they were often changed. Mine has the wrong one in the photo. I will include a photo of the correct mag. Chances are good if it has this one it is an 18-27
[img:3s2ssvbg]http&#58;//i133&#46;photobucket&#46;com/albums/q63/sidmabb/1935%20Oliver%20Hart-Parr%2018-27/guageslinkage-1&#46;jpg[/img:3s2ssvbg]
[img:3s2ssvbg]http&#58;//i133&#46;photobucket&#46;com/albums/q63/sidmabb/1935%20Oliver%20Hart-Parr%2018-27/model80governor&#46;jpg[/img:3s2ssvbg]
[img:3s2ssvbg]http&#58;//i133&#46;photobucket&#46;com/albums/q63/sidmabb/1935%20Oliver%20Hart-Parr%2018-27/Magneto%20needed/dual1&#46;jpg[/img:3s2ssvbg]
[img:3s2ssvbg]http&#58;//i133&#46;photobucket&#46;com/albums/q63/sidmabb/1935%20Oliver%20Hart-Parr%2018-27/Magneto%20needed/dual2&#46;jpg[/img:3s2ssvbg]