5.0 Resto 1979-04 Mustang Front Seat Brace Repair Plate Kit | Install

In this article, we’re going to be taking a closer look at our 5.0 Resto front seat brace repair plate kit and how you can fix your damaged brace without replacing the entire piece. So the topic for today is torn seat braces and how you either fix the damaged brace or prevent future damage from happening.

The seat brace is a spot-welded piece underneath the carpet that spans the width of the floor pan. It adds structural support to the car and also houses the front studs for the seat track. What we’ve experienced with several cars that have come through the shop is that the metal around the front studs will begin to tear causing the seat to feel loose and expose a safety concern. Like anything, some cars are worse than others and this typically only happens on the driver side.

Until today, we’ve had to replace the entire seat brace to fix this problem. While that is still completely valid and of course needed given the severity of the damage to the seat brace, we knew there was an easier method for this and we figured out a solution with our 5.0 Resto seat brace repair kit.

Repair Plate Kit Breakdown

• The (2) repair plates are constructed in the USA with a heavy-duty 1/8” steel plate that is precisely bent and laser-cut to ensure a great fit over the seat brace.
• Each plate is side specific and the way that you know which side is which is by looking at the rounded edge on one side of the plate. This will be positioned towards the inside of the car and will only allow these to work on their respective sides.
• These plates can be welded into place or they can be secured with the provided M8 “through-bolts”. We feel that the majority of you are going to bolt these into place, but if you do choose to weld these, make sure you remove any paint and/or coating from this area to ensure a good weld.
• These will raise the seat about 3/16 of an inch so if you're on the tall side, you may have to go back one notch on the seat recline position.
• The last thing, if your seat brace is beyond repair, well, you’ll obviously have to replace the entire piece, but you can install this kit as added insurance for the new brace.

This Kit Contains:

• driver and passenger side repair plate
• long through-bolts
• lock nuts for these bolts
• j-nuts
• seat track studs, nuts, & bolts

Tools Required

• socket set
• drill
• 3/8" drill bit
• marker
• push pin removal tool
• body saw or cut-off wheel to clean up any deformed metal
• medium-sized pry bar
• (2) 15mm open-end wrenches
• small-handled sledgehammer
• dead blow
• block of wood
• cleaning supplies

Throughout this process, you’ll see us use an assortment of other tools that we didn’t mention. Like any project, some require more tools and some don’t so just make note of something that you see us use. If you’re welding these, you need proper welding equipment and supplies.

This kit will fit all 1979-2004 Mustangs with the only call-outs being that the fuel relay bracket on 1986-1991 cars may have to be bent accordingly to clear the bracket and any wiring harness near this area may have to be repositioned alongside the seat brace. We have a really good example in the shop today to show you guys because the seat brace on the car we’re going to be working on is COMPLETLY ripped out.

1. First, you’ll want to remove the front seats followed by any interior component that will allow you to roll the carpet out of your way. These include the scuff plates, kick panels, and center console. Then you can simply roll the carpet to the rear of the car. We’re going to be starting on the driver’s side, but you can start with whichever side first.


2. If applicable, loosen and remove the (2) bolts that secure the ground wire and the fuel pump relay bracket.


3. Dislodge the harness clips from the brace and then position the harness out of the way.


4. Depending on how damaged your brace is will dictate the next few steps. Ours was pretty messed up so we had to cut away some of the deformed metal with a cut-off wheel and a body saw with a metal blade.


5. We also used a heavy-duty chisel and a hammer to separate the damaged metal from the seat brace since some of the metal is multiple layers. A pair of needle-nose pliers were also used to help grab the metal and pull it away from the brace.


6. Now we need to ensure the brace is as flat as possible. Position the correct plate over the seat brace. Tap it with the dead blow until it’s fully seated.


7. Take the block of wood and work your way across the plate striking the wood with the mini sledgehammer.


8. Use a pry bar to lift the plate off of the brace and inspect the brace to see if you flattened it out. Repeat this process as necessary.


9. Whenever the brace is nice and flat, mark the (4) holes that need to be drilled with a marker.


10. Center punch the mark.


11. Remove the brace and carefully drill all (4) holes with a 3/8" drill bit and then debur each hole. Clean up the metal shaving and wipe down the area if you want to.


12. Because the outermost stud was ripped on this car, we’re installing (1) of the provided j-nuts into the small provision in the plate. If both studs are ripped out on your car, install both of the j-nuts.


13. Position the plate into place & slide (2) of the long bolts through the plate and seat brace.


14. Install (2) of the provided locking nuts and fully tighten. Do not overtighten this hardware.


15. If applicable, reinstall the fuel pump relay bracket and the ground wire. Reposition these accordingly so that they accommodate the repair plate. Some of the harness clip provisions may be covered by the plate so route the wiring harness alongside the seat brace.


16. Thread the provided stud into the j-nut by hand as far as it will go. The stud is symmetrical so the orientation does not matter.


17. To fully tighten the stud, take (2) of the provided nuts and use them as a jam nut assembly. Thread on (1) of the nuts followed by a second and tighten these nuts against each other with (2) 15mm open-end wrenches.


18. Rotate the top nut with the open-end wrench until the stud is tight.


19. Loosen the jam nut assembly and remove the nuts. Do this for the other stud if needed.


20. Repeat these steps for the other side. Even though our passenger side was fine, we’re using this opportunity to install the repair plate anyway so that it matches the driver’s side and for peace of mind.


21. Once both repair plates are installed, reposition the carpet and reinstall any interior component that was removed or repositioned.


22. Reinstall the seats back into the car and use the provided hardware to tighten down. You will use a 15mm open end wrench for the nuts and a 13mm socket for the bolts and then you’re good to go!

This is a really good problem-solving and time-saving kit. If you’re concerned about a little bit of surface rust on the plates, feel free to paint these if you’d like. Because of the location of the seat brace, these will take a few hours to install, but the steps are really easy and so worth it in the end.