Is it safe to retro-fit standard retractable seat belts on a 92 Subaru Legacy?

My wife’s Subaru Legacy passenger side automatic seat belt finally gave out. The replacement parts for it are going to cost us $900 for the parts alone. I’ve been looking around and there are websites that sell retro-fittable seat belts for what appears to be vehicles much older than our car… or myself. To install these, I would obviously attach them at the current mounting bracket for the lap belt, but would need to figure out how to attach it to the same position as the automatic belt when it locks into place. Has anyone tried this before? Am I just crazy?

I’d just start hitting the salvage yards, eBay, Craigslist, etc. for the orginal rather than go the retro-fit route.

The Pull A Part yard here gets about 10 bucks for a seat belt. Some major metro areas often have a similar yard so that may be worth a shot.
At 900 dollars, no way.