My original chrome buckles are beginning to rust slightly. The rest of the entire rear seat (shoulder) unit is perfect. I found mint buckles I want to swap on my seatbelts. Is it possible to swap just the buckles?

I popped the plastic beechwood color cover off the buckle. The seat belt is wrapped around a long rectangular metal piece in a "u" shape. The seat belt (and floor mount) slid thorough one part of the buckle, but the other side doesn't give enough clearance to make it though since the seat belt bunches up around the floor mount. The only way I can think to swap buckles it to take the stitching out to remove the floor mount from the buckle, slide the seat belt though, replace the buckle, and resew, but (1) I can't sew and (2) I'm worried about safety issues.

I'll post pics soon to help visualize this since it might be confusing to follow the above if you haven't tried to do this. I've also tried removing the rectangular piece in the buckle by sliding it to a 45 degree angle, but it barely won't make it out of the buckle. It is this piece that prevents the seat belt from coming out of the buckle.