Subaru WRX STI GDB model seats are a good choice. They are not as wide as the original Datsun buckets and can be installed without cutting out the Datsun front bulkhead/web where OEM seats mount. Note that together this bulkhead/web and the doubler plate a little further back (integrated into the floor) are both important to structural integrity of the vehicle: they distribute stresses across floor, and two structural elements that importantly add strength and stiffness to the vehicle, they being the transmission tunnel and outer sill box section. The bulkhead/web should NOT be removed, as this will weaken the vehicle. Retaining the bulkhead/web and utilising the other OEM seat mounting holes and seat belt mounting points, albeit with some modification, makes the less likely to unfavourably attract the attention of engineering certifier or vehicle inspectors.
I wanted seats that gave greater front-to-rear adjustment than the originals, they had to be firm and comfortable, driver side height had to be adjustable, and had good bolsters for lateral support. Installing these turned out to be something of a chore, but the final result was seriously well worth the effort. I know that going to this much trouble will not be for everyone, but if you choose to do something similar, reading this posting may save time and headaches.
The seats provide same seating height as originals, though you are unlikely to be able to remember what the original seat height was when your Datto 1600 was new, because the old springs in the Datto seats would have have long since sagged. Seating position of the installed STI seats seems higher, but it is not.
The approach involved trimming down three of the four corner mounting brackets, but not the inboard rear. The inboard rear one was retained because this is particularly strong and Subaru deliberately integrated the seat belt mounting into the seat. In my case, I am using the original Datsun floor attachment point for the inboard rear seat mounting point as well as to attach the Subaru seat. After trimming the Subaru mounting brackets (and enlarging a hole in the inboard rear one), 16mm CrMo tubes were welded front and rear to ensure seat rails would be fixed together, and located relative to each other. Note that without these tubes it is hard to get exactly the right spacing between rails, and it makes the whole installation stiffer and stronger.
One bracket for the outboard attachment off the seat to the car had to be fabricated and another for the inboard rear attachment. From an engineering viewpoint it is important to retain the Subaru OEM brackets with as little modification as possible, particularly as they are riveted onto the rails. It is practical to weld to the riveted-on brackets without affecting the rails. Note that riveting is used here because it is stronger and more reliable than welding and allows for steels that are easy to weld to be attached to others that may not be so easily welded or may need pre- or post-weld heating or some other special treatment. In the case of three of the four Subaru OEM mounting brackets, where these were cut down, a steel tab with a bolt through it was welded on to facilitate the seat being attached to the vehicle. All the welding described involved steel parts that could be readily welded without causing problems. Photos tell most of the story.
Details of passenger side are shown. The driver's side is similar, though the height adjusting mechanism makes things a little more complicated. In the case of the passenger side it is very easy to unbolt the rails from the seat and do the fabrication and welding, and do the test fitting without trying to wrestle with the whole seat. However, this was not so easy for the driver's side, so the passenger's side became the test case and when completed it was a matter of replicating the modification for the driver's side. All welds were done carefully with a MIG, but because the driver's side the rails remained bolted to the seat, and a wet towel was carefully located to protect the fabric and foam padding. This ensured that my seats didn't end up looking like Chinese New Year fireworks.
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File comment: Inboard rear mount of Subaru WRX seat is retained. Tube in the left hand side of the photo has been fitted to connect outboard and inboard rails. The hole in the centre of the photo is used to attached the seat to the inboard rear fixing bracket, via a high tensile M12 bolt. In turn the bracket (not shown) attaches to the original Datsun seat belt mounting point and one of the Datsun seat inboard Datsun rear mounting bolt holes
OEM Subaru Inboard Mount.png [ 1.51 MiB | Viewed 5958 times ]
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File comment: A bolt is welded to a piece of flat steel and this is then welded to the cut down bracket on the Subaru WRX seat rail
Mounting Tab, Fixing Bolt and Cross Tube Welded to OEM Rivetted Bracket.jpg [ 1.45 MiB | Viewed 5958 times ]
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File comment: This bracket is fabricated out of a piece of tube with three tabs for bolts. The one in the middle has a captive M12 nut which is on the side closest to the transmission tunnel
Inboard Rear Fixing Bracket.jpg [ 1.5 MiB | Viewed 5958 times ]
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File comment: This bracket is made out of square section steel tube and an angle. This allows (modified) original mountings to be used.
Outboard Fixing Bracket and Attachment to Chassis.jpg [ 1.57 MiB | Viewed 5958 times ]
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File comment: This is the front left seat rail assembly with cross tubes fitted front and rear. Inboard rear fixing bracket is not installed in this view.
Front Left General Fixing Arrangement - less Seat Belt Mount Bracket.jpg [ 1.58 MiB | Viewed 5958 times ]
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File comment: Seats are installed secure and strong: no problems with getting this engineered, which is a legal requirement in most or all States and Territories. For the weight conscious, taking into account bits that were trimmed off, less than 1kg was added to the total weight of each seat.
Seats Installed.jpg [ 1.8 MiB | Viewed 5958 times ]
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Last edited by AlanDatsomefun on Fri Feb 12, 2016 9:43 am, edited 12 times in total.
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