Antenna is not threaded

The latest "surprise" putting my 70 Duster back together. I found a nice antenna mast a while ago and decided to do an easy job for a change with "no chance of anything going wrong" by just screwing the darn thing into the base, only to find that the base does not have threads.
Looks like maybe the mast just presses into it or something. I had a '67 Dart parts car a while back and I'm wondering if I used the base/cable from it, as another post says something about 67 being the only year that's not threaded. The cable attaches to the base at a 90 deg angle, not straight.
What do I need to look for to get the right base, and does anyone want to trade? Thanks !