seat belt compatibility

Hi, i have a 73 Duster that originally came with a bench seat, im changing that to buckets. My question is if i change the 73 retractible seat belts and replace them with say 68.69,70,or 71 retractible belts will they work with the original 73 belts? the 73 retractible unit is very large and now that i have buckets i'd like to use a smaller earlier unit if i can... thanks Rich