I've done the same thing to my 100 as _DX3_ posted in his response. I didn't use a stainless steel drive shaft. The material I like to use is 4140 grade material. I replace the rear pin that holds the clutch spring in place with a split collar. The hole thru the driveshaft is a weak spot.
Another area I would strengthen is the clutch fork mount with the one that IHinIN sells
http://www.onlycubcadets.net/forum/s...ad.php?t=14116
plus I would beef the area that holds the clutch fork mount on the tractor. Next 70/100 I do will have this done to it.
Make sure your throw out bearing and clutch release lever are in good shape.
Last area to look at is the pilot bushing and pins in the clutch driver. If there is any doubt...replace them.