How To Fit Cobra GT3 Or GT4 Historic Seats Into Your 1976 Porsche
Seat fitting guide
If you own a Porsche from the mid 1970s and want a seat that holds you better without spoiling the period look, Cobra's Historic range is where we start. The GT3 and GT4 Historic are fixed back bucket seats shaped like the competition seats of the era, but made new.
This guide explains how the two seats differ, who they suit, and how they fit a 1976 Porsche on a Cobra direct fit frame, which comes with its sliding runner included.
- The GT3 and GT4 Historic share the same shell, bolt pattern and sizing
- The difference is the trim: the GT4 adds basketweave, leather and bespoke options
- Both suit drivers under 6ft with a 32 to 36 inch waist
- Both take a four point harness only, and are Road and Track, not FIA
- Cobra's Porsche frames for 1973 to 1984 cars include the sliding runner
What is on this page
The GT3 and GT4 Historic
Cobra’s Historic seats are made for classic and historic cars, where how the interior looks is part of the point. Both are fixed back buckets on a steel frame, with an integrated headrest, and both are hand trimmed in the UK.
The two seats share the same shell, the same base mount bolt pattern and the same driver sizing, so they hold you in exactly the same way. What changes is the trim. The GT3 Historic is black vinyl, with a choice of anthracite or silver eyelets. The GT4 Historic adds basketweave centres, soft grain leather and bespoke colour combinations with matching or contrasting piping and stitching, with anthracite eyelets.
Who they fit, and what they are for
Both seats are listed for drivers under 6ft with a 32 to 36 inch waist. If you are taller or larger than that, tell us and we will suggest something else, as a seat that does not fit you is no use however good it looks.
They take a four point harness only, with no six point routing. That is fine for a fast road car and for historic racing where four points are accepted. They are Road and Track approved, not FIA homologated, so if you race, check what your class requires before you order.
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The Cobra frame for your Porsche
A 1976 Porsche falls in the span Cobra cover with their frames for cars built from August 1973 to September 1984. There is a frame for the 911 and a frame for the 924 in that span, and Porsche changed the cars in October 1984, so the frames do not swap across that date. If your car is anything other than those two, or you are not sure, send us the chassis number and we will confirm what fits.
The frame bolts to the factory mounting points in the floor with nothing drilled, and it comes with a sliding runner included, which most other frame makers charge for separately. It takes Cobra base mounted seats with the 291mm by 330mm pattern, which is what the GT3 and GT4 Historic use. Each frame fits one seat, so order two for a pair.
Fitting them
Take out the original seat, bolt the GT3 or GT4 to the runner on the Cobra frame on the bench, then bolt the frame to the floor. The frame is a safety part: it carries every bit of load your body puts through the seat in an accident, so torque the bolts to specification, not by feel. If you do not own a torque wrench, that is the one tool to borrow before you start.
Garreth’s advice on a car this age is to lift the carpet and look at the metal around the seat mounting points before you order anything. For more classic Cobra options, see our guide to Cobra special edition seats and the cars they suit.
What is the difference between the Cobra GT3 and GT4 Historic?
The shell, bolt pattern and sizing are the same. The GT4 offers more trim choices, including basketweave, leather and bespoke colours.
Who do the GT3 and GT4 Historic fit?
Both are listed for drivers under 6ft with a 32 to 36 inch waist.
Can I use a six point harness?
No. Both seats take a four point harness only.
Which frame fits a 1976 Porsche?
Cobra make frames for the 911 and 924 built from August 1973 to September 1984. Send us the chassis number to confirm.
Do Cobra frames include runners?
Yes. The sliding runner is included with the Cobra frame.
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For a period interiorThe GT4 Historic
The same seat as the GT3, with the trim options to match a classic Porsche interior.
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