I'd measure the belt. Pull it all the way out and measure the length. Then compare with what you find at the pick-n-pull.

I've learned a few things...

Drivers side belt is usually longer than passenger side. Dunno why. However I made my wife more comfortable in my passenger seat by swapping in a drivers side belt from a junker.

Various changes in belt clip/buckle design over the years. Pay attention before removing from junker.

Opening the case (located at base of B pillar behind drivers door) and cleaning up the innards can help bring a sluggish belt back to life. It's been a long time since I had one open. As I recall there are two widgets that lock it from unrolling. One is a "speed of belt pull" thing. Pull fast and it locks. There's a rotating wheel with angled teeth, and something (sort of a blade) jams against the teeth to look the spool. I did something so the blade doesn't jam the teeth quite as easily. I think I bent it back a bit but I can't exactly recall. You'll see how it's built when you look inside. I did the same on a few of our belts over a few years span, and it worked well. Testing with a fast pull afterwards proved that it would work properly in an accident. I also cleaned up any dust and grime inside.

The other spool lock is a tilt sensor (basically a weight on a pendulum) that locks the belt from unrolling. Not much to do there, except remember when testing the unit while holding it in your hand. If you tilt the assembly it will lock.

Good luck with it!
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Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.