Is there a way to tighten up the spring so the seat belts will retract on their own, and/or, is there another seat belt from any other Porsche model that maybe would work in a 914 as well?

I offered to tighten springs for $20.00 a pair last year. Offer still open. You pay shipping both ways See This Thread

The web material needs to be in decent shape or no amount of tightening will fix them.

I seem to remember that people were also using 924/944 seatbelts, though I have never seen it personally.

If the belts are in good shape, that $20 tightening seems like a great deal. You don't want to take these things apart unless you really know what you're doing as the spring likes to go "sproing" all at once!

And if you think you really want to try see this.
http://www.914world.com/bbs2/index.php?sho...=107866&hl=