I agree about belts in general, but based on the dynamics of this collision, very little extra load was placed on the one belt in use, the driver's. I would not discourage you from replacing it, but wanted you to know it was the only one in use during the collision and that the primary acceleration of the driver was rearward, not forward.
That rearward load appeared to have severly weakened if not broken the driver's seat back.
I would also agree on not using that center rear belt anymore.
Oh, and if nobody mentioned it, each of those SECCS stickers is worth +5 HP...
Also, I don't recall if they sold or not, but there were a set of ski racks, and possibly stock wheels sitting around that went with that car if you are interested, but you would have to ask Debbie.