sealt belt question/help i cant drive
 

I just replaced my driver chair on my 84 300d with another chair form another w123 same year,now my seat belt won't buckle,i take it they are different,what are my options?
will i need to unbolt chair and take it out again in order to remove pillar(female part) in order to change the bottom part,i really do not want to change the belt because that mechanism always gives me trouble,help please anyone,i cant drive without my seatbelt.
Thanks