I will respond on this since I have been a certified parachute harness repair person and used to be certified to build seat belt sets (but the liability insurance got way too high so I dropped the certification). All auto seat belts are nylon webbing with a minimum of a 4000 pound breaking strength. Seat belt material is nominally 2 inches in width with some of the newer cars coming out with both wider and narrower materials. Generally auto seat belts come in a very low range of colors due to the cost of custom colors and minimum purchases. How many stock cars do you see with yellow belts?
Many upholstery shops can replace seat belt material for you, or you can gather the materials and find a local sky dive club and find out who does their harness repair. When I was actively reparing parachute and aircraft harnesses, I used to replace many car seat belts with custom colors and buckles. Take a close look at the sewing on stock seat belts. It is minimal at best. No parachusist would ever go aloft with such poor sewing techinque. A good sewing machine can sew a number 92 or 138 thread with a strong zig zag pattern that will hold long after the actual webbing fails. (One of the true tests of a harness repair person is to have them jump using one of their repaired or custom harnesses, truly builds trust in your work!) Lifelines on sailboats use the same technique, I have fabricated hundreds of sets of lifelines that have been inadvertently used many times with no failures. (Sailboat lifelines are traditionally one inch tubular nylon webbing, which is actually 2 inch flat webbing woven into a tube.......)
Also, seatbelt material makes great towstraps for Fieros. My brother has a number of seatbelt material towstraps for all of his Fieros. The natural stretch of nylon helps reduce the shock of starting and when some of us over run the strap. In fact, on some they stay almost permanently attached, some fore and aft. Never can tell when you will need a tow....
I carry a custom tow strap for my 87 GT (a matching purple strap) all the time to prevent having to use a chain or other destructive tow device. I have also towed a few other small cars in emergency situations. Check eBay for "nylon webbing" and you will find a large selection of varied colors and sizes. Alway look for 2 inch wide minimum, all nylon webbing. Never ever use anything that is poly or partially poly, it will fail very easily.
I have replaced all the seatbelts in both my 87 and my brother's new project car (88 Formula/GT) with new webbing material and extras, just to look different and to upgrade the old material. Find an extra seatbelt mechanism for a Fiero and take the big black plate off. Carefully pull the seatbelt out to the very end. Notice a small rod jammed into a slot in the rotating retractor center? If you jam the retractor so that it cannot spring back, drive the small pin out and install new seatbelt material in place of the original, you can feasibly change to any color with no real problem. If you are worrying about the safety aspect, take a look at the retractor mechanism before you take anything out. With the mechanism still attached to the car, pry off the large black plate and pull the seatbelt out to the point where it would fit you with a little to spare. Notice that there are still at least 3 wraps around the retractor core? This is the actual stress location that is impacted, not the small pin jammed into the slot. As tension is placed on the belt, it merely tightens around the center of the retractor and compresses around the remaining seatbelt material on the rotator. This is not the same concept as racing harnesses or parachute harnesses, they must be fully sewn clear to the very end of the belt that attaches to the floor board or parachute.
Many Fiero folks are tempted to change their belts but are concerned about the liability issue if they are in a wreck and someone looks at their seatbelts and finds no certification number label. That is a valid concern, but somewhat limited. Show cars are obviously an exception and I have replaced many sets of belts with new colors and buckles for a better look.
You can also dye the nylon webbing without taking it off the retractor if you are really inventive. Take the whole thing out of the car, prepare a large bucket of very hot water and Rit black or Navy blue dye. Immerse all but the retractor mechanism for at least 4 hours and keep the water/dye solution as hot as possible without boiling. Best done on a stove top if no one is looking. My first purple belts were originally the light grey 86 Fiero belts that took about 5 hours of dye work to change to a nice purple. Rinse in cold water at least 7 to 9 times to get the dye out, otherwise you and your passenger will have colored strips across their midrif for the first few wearings.
Any good marine canvas repair person can stitch the buckles and ends in place for a very nominal charge. I used to charge $5 to sew new seatbelt material onto old or new buckles. If you can't find a marine canvas person check out awning repair or sales locations they generally sew their material on site and have large heavy machines available to do repairs.
Didn't mean to get carried away, just wanted other Fiero folks to understand that there are alternatives to their stock color seatbelts. I can be reached at my normal email address of Tami@V8-Fiero.com if you have specific questions.
