Hi,
I've not got seats for my car yet, but have been researching quite a bit. My TR4 will be set up for street primarily, but I would like to take it autocrossing a bit, too.
You need to carefully read the rule book to see what's allowed in the type of racing you want to do. SCCA has different safety requirements for different types of racing and sometimes for different classes within each type. In general, a fixed-back (one-piece) seat will be necessary. In some cases, a 5-point or 6-point harness is needed. Certain classes require non-adjustable mounting and/or a seatback attachment brace to the rollbar.
I like the Corbeau classic for TR250/5 and earlier cars, with the headrest. It's a fixed back (one-piece) seat, so should qualify for vintage racing and probably would be acceptable for some SCCA events. Since I will be recovering the seats in my car anyway, I've been looking for a used set of these or the old, original Corbeau GT seats (NLA).
The Corbeau Clubman might be a good choice if you want a more modern style seat. It's not very wide at the shoulders.
Both the Classic and Clubman are quite tight fitting at the hips, so consider that before buying. Try on a seat locally if at all possible.
I know for certain the Clubman is, and think both these seats are prepped for 5/6-point harness required in some SCCA events (and, AFAIK, no y-type shoulder harnesses allowed by SCCA).
Corbeau Classic seem to run about $250 apiece new, in vinyl or cloth trim (leather is alot more), and the Clubman is about $225 apiece in same trim options. In either case, mounting brackets are still needed and are an additional cost. Not sure if Corbeau offers one specific to TR6 (I know they don't for TR4, which is very similar in the tub where the seats mount). Custom made brackets or modified universal brackets might be needed.
If you want adjustability, better check the rule books. I know Summit Racing sells an adjustable seat bracket that's NHRA legal (double locking), not sure if it would pass muster for SCCA though. Many single-locking adjustable sliders won't get past a safety inspection. Many competition prepped cars have fixed/non-adjustable seat mounting, anyway.
If you decide one of the Corbeau seats is what you want, search the Internet for sellers. Some offer free shipping, which can be a very significant expense with seats.
www.corbeau.com has lots of details about the various models available, and is divided into fixed-back racing seats and "street" seats. Seat dimensions are provided.
Some of the Cobra seats you mention are very similar to certain Corbeau models. Enough so that I've wondered if it might be the same manufacturer marketing under different brand names in the U.S. and UK/Europe.
I've not seen any Recaro, Sparco, APC, etc. that I felt would work or look right in my ca. Some of their seats are excellent, but all seem to offer only a choice of very modern/hi-tech (wide-shouldered, as you say) racing seats or "street" seats that recline and tilt.
Kirkey is focused on aluminum seats, some of which can be fitted with minimal covers. Certainly an option that can provide very good driver fit and security, but at the cost of comfort.
Another option, relatively inexpensive, is the plastic buckets available with and without snap-on covers from a wide variety of sources. Some would fit, and are available in low-back or high back designs. Heck, seems everyone has these: from Summit to J.C. Whitney to my local Kragen. Pretty common looking, but some models might be adequate if money is an issue. Do check rule books before installing, though.
There are some specialized manufacturers of off-road seating, and most of the major seat companies mentioned above offer this type seating in their lineup. However, offroad seats are too wide and seat the driver too high for our cars.
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