You also need the piston pin and 175 small end bearing...  bearing is different on 175.

Hang on a sec, so i been wondering this myself because i have a 73 AT125 that is just...ugh lol. What i have planned to do someday is take the stator off a CT175 and bolt it right onto the 125. If these both use the same crank shafts there should be no need to buy a 175 crank unless im missing something? i believe the cases are the same too but id have to have both in front of me to tell.

The crank stub on the ignition side is different on the AT.  Shorter taper and internally threaded that uses a tiny bolt to hold the armature vs. the CT that has a beefy threaded end and takes a nut to hold the flywheel.

Someone has put a CT ignition on an AT crank but it requires some hokey mods (in my opinion and we know what opinions are worth) like notching the point rubbing block. If you search you can probably find the thread.

Changing out the crank is the best way to go or get the VAPE CDI or something like it.

 

Gotcha! thats really good info to know, i hope some day i can do something with that bike. As it sits the whole lower end is shot and the top end needs to be done. The armature looks worse then the one in a previous post.