Hey Steve - you just gotta get this stuff figured out. IH changed to a wide frame so the 14hp and 16hp engines would fit (instead of using that notched frame like they did on a 147), So, the only way a K321 (14hp) is going to fit in a 122 is if you change the flywheel and shroud to the 12hp version (as has been stated) or if you cut up the frame to allow the original flywheel and shroud to fit.
Now, I really don't agree with Dave's opinion on a 109 vs. 147, but to each his own. If I had my choice of these 2 tractors I'd take the 109, primarily because I just don't like the electric lift that was standard on the 147. And the 147 doesn't have the center removable frame cover. The only other thing going for it, is that it has lights as standard. Now, a 109 is a nice tractor, light weight hydro with the 10hp engine (and the funky green stripe hood decal). You can drop a K321 (14hp) engine directly in place of the 10hp as long as the K321 has the correct base, and hopefully the correct crank for the S/G basket pulley and PTO. The 109 is standard with armstrong (manual) lift so it won't have a ported hydro pump that you would have on a 149 and that you need if you want the infamous CC wide frame HYDRO Lift. So yes, there are pros and cons between the 147 and 109. If I was you and the 109 needs a replacement engine I'd certainly be looking to drop in the K321, and I'd be looking for a ported Hydro pump and all the HYDRO lift parts, and the headlights and tail lights so you could make it one of the best Cub Cadets ever built - THE 149.
That's my story and I'm sticking to it.
And one more thing. You started this thread looking for a Crank for a K321 (14hp). You do need to make sure you get one that is for a Cub Cadet design. The Part No. is KH-45-142-25. It's also the same crank used in the 16hp Kohler K341 for the Cub Cadet 169 and 1650. (I did see a place that has a brand new one for $600. That is EXPENSIVE).