Jim Smart
October 1, 1998

Step By Step

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We used a ’65–’66 Mustang taillight gasket as a template before we started cutting. The gasket opening should be placed exactly 1 inch from the taillight opening already stamped in the panel.
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Accurate measurements are critical. You don’t want to make a bad cut. Taillight openings are to be spaced 1 inch apart as shown.
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Before you cut, lay the T-bird taillight trim in place over the markings and center it perfectly, then mark the screw holes.
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First, drill a 3/8-inch hole at each corner, which is where cutting will begin.
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We used a fine-tooth jigsaw blade to cut the openings. Always wear eye and ear protection.
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Work the saw blade around carefully until all four corners are reached.
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T-bird taillight lenses and trim for this project came from Larry’s Thunderbird & Mustang. All you will need are the lenses, trim, and gaskets. We have six used ’65–’66 Mustang taillight reflectors clad in Eastwood’s cad-plating paint, which are being retrofitted for this job.
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If you haven’t acquired new ’641/2-style taillight reflectors, you can pick up a set of used ones and restore them with Eastwood’s cad paint. Our source for light sockets was the local auto parts store. You will need six sockets designed for a #1157 bulb.
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Once the original socket has been driven out of the reflector, scribe out a perfect 1-inch circle around the existing hole.
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Take a die grinder or cutter and open the hole up to the 1-inch circle.
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Pilot holes that have been drilled for reflector retaining screws must be countersunk as shown with a 1/2-inch drill bit. Don’t drill too far or you’ll go through the metal.
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The modified ’65–’66 Mustang taillight reflectors are fitted from the inside using body rope caulk as a sealer between the reflector and the body. Use a stainless-steel countersunk screw with both a flat and a lock washer inside.
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Our installed trio of Mustang reflectors look like this. All we have to do now is wire in the sockets. You can tie the sockets into the stock wiring harness and plugs. We suggest you use a brake light relay, as the addition of four bulbs creates a greater electrical load.
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The lens is next, using the gasket included from Larry’s Thunderbird & Mustang. Use weatherstripping adhesive to bond the gasket with the lens. A warped tail panel will crack the lens, so be careful when you’re tightening the screws.
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Finally, install the die-cast trim pieces, again taking extra care to prevent cracking the lens.
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The finished product looks like this, with a factory-original appearance. All we need now is that ’70 pop-open gas cap.

Customizing a classic Mustang dates back to 1964 when the first examples came roaring down Main Street. Nearly every customizing trick known to man has been tried on a Mustang. Taillights are a popular area for customization. We've seen Cougar taillights, three Mustang taillights on each side (yuck!), and even Camaro taillights used in the quest for individuality. We were stung by the taillight bug, too, on our '65 5.0L EFI coupe project.

We kicked around several customizing tricks. Ultimately, our choice was '64-'65 Thunderbird taillights from Larry's Thunderbird & Mustang parts. T-bird taillights were good enough for Ford on the '68 California Specials, High Country Specials, and Shelby Mustangs. Why not on our humble project? Here's what we learned through our customizing efforts. Thunderbird taillight lenses and trim are widely available for T-birds and Mustangs alike. The light assemblies, however, are not. T-bird taillight assemblies are only available used, and there aren't that many of them around.

Our solution for this dilemma was to use six '65-'66 Mustang taillight assemblies. You can source these new or used. If you're going to source them new, opt for the early '64-1/2 design with pigtails and plugs for easy installation. If you're going to source them used, keep reading. We'll show you how to modify them for aftermarket sockets and wiring, then how to tie them into your Mustang's electrical system.