I have a 72 that was originally a malibu. what kind of seatbelt retainer should i have. the chrome clips or the plastic retainer that is kinda like a shelf?

I have a 72 and it came with the plastic "shelf". Do you have a pair?

I have the "shelves" Yes. I have left and right. How do they mount? I mean. I've done all of my own headliner work and would like to put these things up in the correct manor.

Small, self tapping screws - flat head - or pop rivet. I went the screw route, the plastic headliner trim that runs the length (back to front) will cover the screws.