Hey
bvanzalen Sorry i missed this when you asked a question. Don't know if you still need help or not but you would have to disassemble the P.T.O. to replace the button. I just switched my 169 over to the early style button and changed from the brake style lever to the wear button lever. here are a few pictures to let you see what you would be getting into.
This is just putting the P.T.O. back together. Getting it off and to this point was a bit of a fight.
Once everything is apart you are just starting with the pulley.
Add the springs, making sure to line them up as shown.
Then the thrust button. This is the early style. Yours would have the nub sticking up with the groove for the snapring.
Then the levers and bolts. Then it gets a little tricky. You have to grab all of this and keep it together while you turn it over.
This is what it looks like when it is flipped over.
Then add the clutch disc.
The 3 release springs.
And the pressure plate.
You have center the clutch disc and line up tabs with the set screw holes.
Then this is the way i hold it while i adjust the tension on the springs.
You just barley snug the vise just enough to keep the nuts from spinning. This way you are not trying to hold everything together, keeping the disc centered, and trying to hold a wrench all at the same time.
This is what it will look like before you start adjusting.
Then you just bring them down a little at a time till the gage just touches the same in 3 positions.
If you get a rebuild kit it has good directions. but you get the basic idea here.
Hope this helps.