Pulled the left front seat belt assembly from the Lachs Beast yesterday preparing to do this today.
The Kelvinator had no belt latch button to keep the latch from falling to the floor - where it's a PITA to pick it up every time. I figured I'd swap the belts.
Well, today as I was picking up some other stuff, the rubber seal for the front door parted company with the welting around the door and I discovered it's not a press fit; it came unglued. So I once again poached a good rubber part off the Lachs Beast to replace a bad one on the Kelvinator. In the process, I unscrewed the B pillar cover to get the welting off - and to replace the belt. Had the Lachs parts been good, I might have swapped the whole thing as a clumsy, but complete, assembly, but the latch had been slammed in the door breaking the edge of the trim panel in the parts car, so I slid all the parts out of it. They do fit through the hole.
As always, though, the 'butcher' had broken something inconvenient. The plastic slot cover where the belt emerges from the pillar trim cover had holes busted because someone doesn't know how to tighten screws properly. This meant that the belt had to come off the retractor reel. If you've ever changed the tape in a measure, you know how this goes. You have to unreel it all the way and then DON'T LET GO or it'll unwind the spring and then, good luck getting back the proper number of turns. When I got the belt all the way off the reel, it looked to be simply inserted through it. So I gathered a little slack and pushed it further through the slot. Lo and behold, an elegantly simple thing: a short plastic lug is inserted through a sewn loop at the end of the belt. Push the lug out and the belt can be withdrawn through the slot. [Right here, you'll notice a plastic sliding slot thing that's part of the retractor assembly. It comes out by lifting in the center so it comes out from under the slots on the sides. Since the sewn end won't fit through it, it stays with the belt.] Once that's out, you will want to stick a screwdriver into the slot so it doesn't reel up. I did the same thing to the other belt and then assembled the good cover onto the belt with the good latch button and put everything back through the good pillar trim cover. So now, when I reach for the belt latch, it'll be where I expect it to be.
Now, the grill looks out of place when compared to the rest of the trim. Looks like I'll eventually be renewing it all 
