Seat Belt Help

Anyone have specifics on 1971 Dart seat belts?

Can someone help describe what I'd need to order
- i.e.....
- How many belts do I need?
- Required lengths?
- Recommended source to purchase from?

Note: I'm a bit confused by the 3-point retractable belts you see on-line. I've got a two-door coupe. Was this style belt part of a 71 Dart Swinger configuration?

Reason I'm asking is I've got a box of mis-matched belts that may or may-not have been in the car so basically starting with nothing.
Any help and guidance would be greatly appreciated 8)