Here is somewhere you can check out...
1971-1974 Plymouth Road Runner Driver, Passenger & Center Seat Belt Kit
)If you replace on your 72 with 71s kind, you’ll miss the seatbelt warning system function and will never stop to buzz as soon you seat on your car and put the key in RUN. Unless you disconect the seatbelt control relay.I am replacing the set in my 72 with 71 style. I bought the set but have not changed then yet. I believe the belts are the same from 72-74. I'd be happy to sell you the set from my 72. They are black.