69 dart how to convert manual to power steering?

I went from power to manual on a Dart sport once, and I locked a vice grip on the shaft and pounded it down until it was long enough, not sure of 2 things: 1.) how much splines were left after I pounded it down; wouldn't want that baby coming off while driving... lol.. it worked fine. 2.) I've never did it the opposite way, shortened it