Tim, That is one of the nicest restores of a 100 that I have ever seen. The 70/100's are one of my favorite as my first cub was a model 70 with a 42 inch deck. I installed a k241 and mowed with it for years. Like a dummy I sold it to my brother and he still uses it to mow ditches with a sickle bar mower.
I am really looking forward to seeing the look on your grandfathers face when he first sees it. Are you going to do a video of him driving it? I bet he would really enjoy it. It is great that you can still enjoy your grand father, mine passed when I was three years old.
Again fantastic job.
Tom