I have done both kits, and the 60-66 type twice. The biggest difference is the 73+ hardware is much heavier than the 60-66 stuff. The balljoints and tie rod ends are beefy on 73+. That being said, 2 of my trucks were driving on original or original replacement parts with no problems.
They claim that the 60-66 stuff is 'hard to find' but I got my last set of upper BJ's at Autozone for roughly 20 bucks and no shipping!!
Used 'em on my disc upgrade on the '66.