How to remove seatbelt?

[GMC"ER]

I have a 69 GMC stepside and working on the interior wanting to dye the seatbelts, researched all the past posts on how to, got that part. Went to remove the belts... the two center belts came out with the center bolts no problem but the two side belts I don't want to mess up the covers as they are in great shape but how do they come out. Underneath the cab I see the welded nut and would assume that they unbolt from the top? But how do you access the bolt? Does the cover slip off? Or does the whole cover and belt housing turn? I am new to these trucks and I don't want to mess up the original coverings on the belt. I know this is a silly question but I have already made some simple mistakes with other parts on the interior and had to replace with reproductions that I was not happy with because original is always better... live and learn I guess. Thanks Robert the newbie.