rear seatbelts in 1981 gti

Hi probally a daft question, can I fit mk2 rear seatbelts into my mk1, only asking as I know for a set, havn't even looked at the setup in the mk1, but will defo have to get seatbelts fitted in the back, many thanks

The Mk1 should already have seat belts in the back, if its a 1981 model.