Fitting Seat Extenders

The seat extension runners were purchased from Mustang Maniac. They allow an additional 2″ or 4″ legroom and retain the stock movement of the seat to adjust on the original runners. These extension kits are made from a heavy gauge steel with threads and cut-outs which allow for straightforward installation with no special tools required. The extension rails are made with the cut out recesses to ensure a flush and tight fit to the original seats rails.

There are four collared studs provided with the bars to allow the repositioned seat to be bolted back into the car without having to cut or butcher the floor pans or seat base.

Depending on your preference you could respray these bars to match your interior as they will be a little more visible as the seat will sit further back. Satin black is always a good starting point.

Removing the seat.

Under the car there are four rubber grommets (there should be) in place where the seat rail studs come through the seat pan.

Remove the rubber grommets and inspect the inside. If all is good the studs won’t be corroded up and will be easy enough to remove. If the rubber grommets are missing and there is corrosion on the studs, then you may need to spray a little WD40 to help loosen up and remove them. Make sure to use a good quality socket, if you round the fasteners off then you are in for a whole heap of hurt.


Fold the back of the chair forward to the seat base as if you were getting out of the back seats. This helps to balance the weight of the seat and allows the fasteners to be removed without the chair tipping back making removal difficult or even bending a seat stud.

Use a deep reach socket to undo the fasteners.

With all four fasteners removed the seat should lift directly upwards out of the car. Notice in the left-hand pic that the seat falls naturally to the rear. Keep the fasteners safe as they will be used again to refit the seat back into place.

With the seat out, now would be a good time to inspect the seat runners and clean up if needed. Apply a little grease to keep the free movement before refitting.

Fitting The Extenders

The bars have to be fitted to their correct left or right hand sides and the right way up. Looking at the seat from below the right hand side has the seat movement handle and a extending bracket. This side will need the cut out sectioned runner to be fitted, as the pics below. You can either attach the studs at this point or later the choice is yours. I prefer to do it later so nothing got in the way.

You will notice that there are holes, recessed holes and threaded holes. The standard holes are to allow flush fitting of the bars to the seat rails where the rivets are. The recessed holes allow for the original seat studs to be held flush to the bar. The threaded holes are for the studs position where you want the actual length of the extension to be.

Below shows the third hole down which is recessed and where the original seat stud(s) will go through.

The top hole is the 4″ extention the second one down is the 2″ extension shown in Red.

Yellow arrow shows the location for the seat rail rivets.

Teal colour arrow shows the seat stud holes.

From the shown position above turn the bar over to fit onto the seat rail flush. Fit the rail over the original seat studs and use some nuts/fasteners of the correct thread on the seat studs and tighten the bars firmly into place.

You will now need to cut the original seat rail studs flush with the top of the nut. This has to be done in order to fit the seat back into the car and be bolted back into place. Before you do any cutting, make sure that the seat can still freely move with the seat adjustment handle with the extension bars bolted in place.

You can either mark the studs for cutting and remove the fasteners and bars away from the seat, or do it with the bars still bolted in place which is easier to be honest. I used a Dremel and a thin cut off wheel. Take your time and use goggles in case the cut-off wheel breaks or sparks fly. Going old school with a hacksaw will work just as well. You can see my Dremel in the right-hand picture bottom corner. I also got pretty OCD about it and ground the studs perfectly flush with the fastener.

Fitting The Studs

These new studs have a collar a quarter of the way down. The shorter thread screws are fitted into the extension bars, the longer thread will be going back through the seat base using the original holes.

I painted the top of my studs to match the bars so they were less visible from the outside.

You will need a locking pair of grips to screw these replacement studs into place tightly, or a strong hand grip an pliers. I also used a little thread locker to keep them in place. The left-hand picture shows the correct stud fitting.

As I said earlier, if you want the full 4″ extension use the top threaded holes, for the smaller 2″ extension use the second hole down. Fit the second stud at the bottom of the rail extension use the threaded hole just above the larger hole (for the rivet) for the 4″ extension, and the 2″ threaded hole is below the larger hole. See the marked up image earlier on the page. If you are in any doubt measure the original seat stud gap and apply the same gap to the 4″ or the 2″ stud holes.

Refitting The Seat

Take the seat back to the car and drop the studs through the original holes in the seat base and carpet holes. From there screw on the fasteners from underneath the car to hold the seat in place. Refit the carpet spacers and then tighten up the seat properly.

Replace the rubber grommets and the job is done.

Sit back in the car and feel the difference the extra few inches gives you.

Update 1st December 2022

Mustang Maniac are now selling these kits at their online Webshop.

You can get them by clicking the image above, clicking here. Or copy and paste to your browser:

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