The correct molding clips are available reproduction. I believe front and rear clips were different as well as a difference in the clips from a 70 to a 71.
I would suggest installing the correct clips for the molding. I think the 71's had a stud rather then a screw.
I am now in the process of installing my windshield with 3m window weld, basically dum dum, which is the way the factory originally did it.
Many people use a secondary sealer around the window to fill in the gap between the glass and the body in the window channel as extra insurance, which I will be doing.
If you choose to use the secondary sealer such as silicone, install the moldings right away.
It is tough to get them to sit right once the silicone cures. Make sure the channel is as clean as possible so that the silicone will adhere.
Good luck with the job. Window leaks are a pain and sometimes difficult to fix.